John McGowan, a burly, fast-talking senior investigator for the UK's National Crime Agency (NCA), was at work one Tuesday afternoon in April 2015 when a colleague passed on a piece of intriguing information.

The French customs agency, La Direction Nationale du Renseignement et des Enquêtes Douanières (DNRED), had received a tip-off that had been communicated to UK authorities: a tugboat with a Turkish crew en route from Cape Verde was somewhere off the west coast of the British Isles heading towards Scotland. It was believed to be carrying a shipment of cocaine. The information was accompanied by a photo of a tugboat named the MV Hamal and details of the vessel's size, weight and colour.

Like most tugs, which operate in busy port areas, the Hamal was painted to be visible: its hull was red and its bridge white. With its green deck, the vessel had the appearance of a jaunty character from a children's book. An average boat of its type moves at around eight knots, which is roughly 15kph, meaning that the area that needed to be searched in order to find the Hamal was, potentially, hundreds of square kilometres. There was a window of opportunity to find it of two, or perhaps three days.



"What we're looking for is a needle in a haystack," McGowan says 16 months later. "We want to find this 35-metre ship - albeit it's bright red - somewhere out in the Atlantic Ocean."


Normally a vessel is identified by its Automatic Identification System (AIS), the tracking protocol that exchanges data with other vessels and shore-based agencies. "It reveals the MMSI number - Maritime Mobile Service Identity - which shows your navigational status, so whether you're at anchor, aground or underway, your speed, position, course over the ground, true heading, International Maritime Organization (IMO) ship identification number, radio call sign, name of the ship, type of ship, draught of the ship, your destination and your ETA," says Captain Nathan Mills, a master mariner and an expert on navigation systems.

VS Hamal's 3,200-kilogram cargo of cocaine had a street value of £512 million NCA

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"It's part of maritime law that a vessel of that size should always have it turned on - it's a safety and security issue; other ships know where it is in the sea. And if anything goes horribly wrong, we know where to look," says McGowan, 56, who is based at the Scottish Crime Campus, a purpose-built, multi-agency facility, 32km east of Glasgow. "The Hamal had it turned off, which we would see as their plan to avoid detection."



The weather wasn't helping the agencies involved in the hunt. April 2015 was unusually dry across the UK. On the 21st, when the NCA started looking for the Hamal, high pressure meant that the majority of the country was cloud-free - except for the north-west of Scotland, which is where McGowan initially assumed any interception of the vessel would take place.



On the 22nd, Chris Pratt, a lieutenant commander at the National Maritime Information Centre in Portsmouth, attended a briefing at which he also learned about the Hamal. With four decades of service under his belt, Pratt's role was to deploy Border Force cutters, the vessels that protect the UK's coasts. He returned to his office and plotted where the Hamal might be according to intelligence he had regarding the boat's position at 9.30am the previous day.

Pratt had marked a series of arcs on an Admiralty chart. Accordingly, a Border Force spotter plane capable of flying beneath the clouds was sent to sweep the four locations where the vessel might break through to the North Sea. At 5pm on the 22nd, the plane identified a boat that it thought was likely to be the Hamal, but with just a photo of the tugboat, the crew was unable to make a positive identification.



The frigate HMS Somerset had also joined the search on the 21st. The Duke class warship with a crew of 185 and a top speed of 28 knots, is designed to hunt for submarines. The Somerset, followed the vessel identified by the spotter plane throughout the night of the 22nd as it passed over the northern tip of the UK and into the Pentland Firth, a potentially treacherous area with powerful tidal flows. However, the absence of an AIS meant that, like the spotter plane, the Somerset was also unable to provide definite confirmation about the identity of the tug.


Meanwhile, a Border Force cutter, Valiant, was progressing north up the east coast of the UK to be part of a potential boarding of the Hamal, spending the night in Peterhead in order to refuel and for its crew to rest.

National Crime Agency senior investigator John McGowan: "What we're looking for is a needle in a haystack" Greg White

Then, at around 9.30am on the morning of Thursday 23, the crew of the Somerset noticed there had been a change: the AIS of the vessel they had been tracking had been switched on. It was the Hamal. Investigators are unclear why its captain had switched it on, but it's possible that the boat had spotted the Somerset and made the decision to comply with maritime law in the hope of deflecting suspicion.



McGowan was nearly a day into co-ordinating the hunt and had dispatched one of his senior investigators, Alan Carruthers, a tall, taciturn man who has been a Customs & Excise investigator since the 80s, to Stornaway in the Outer Hebrides. Here he was collected by a Royal Navy helicopter at around 6pm on the 22nd and taken aboard the Somerset. If narcotics were found on the Hamal, it would be important to have an NCA officer with experience in Scottish law on board, as the crew of the tug would be prosecuted north of the border.

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Pratt calculated that the Somerset and Valiant - which was progressing up the east coast - would be in a position to intercept the Hamal at around 10am on the 23rd. "At that point we didn't know if the cutter was going to make it to a rendezvous," Carruthers says. And there was a further hurdle to overcome: the tug was registered in Tanzania. For British authorities to board, they needed the permission of the attorney general in Dodoma.



At 11am, when the Valiant and Somerset were 160km east of Aberdeen, permission was received from the Tanzanian government to intercept the tug under Article 17 of the Vienna Convention "against Illicit Traffic in Narcotic Drugs and Psychotropic Substances". The commanders of the Somerset and Valiant were given the go-ahead and McGowan informed Carruthers that he had the necessary authority to detain the Hamal.


"When we were about an hour from the Hamal, we boarded the RIBs," Carruthers says, referring to the lightweight, high-performance rigid-inflatable boats that were manned by members of the Royal Navy, Border Force and NCA. "Two RIBs from the frigate, a RIB from the cutter and we steamed towards the vessel." The RIBs approached the Hamal from its stern. When they were around 200 metres from the tug, the commander of the Valiant radioed the vessel to stop.



It's captain obeyed. At 11.17am the RIBs pulled up on both sides of the Hamal and the boarding party clambered on to the stern. "The North Sea in April can be fun, but it was quite calm, which made the boarding a lot easier," Carruthers says.



There was no resistance from the crew. Carruthers, Martin Pownall from Border Force Maritime Command and another Border Force officer climbed up to the wheelhouse and identified Mumin Sahin, 46, as the captain and Emin Ozmen, 49, as his first officer. According to Carruthers, Sahin was calm and followed instructions. ("What else are they going to do? They've got a frigate looking at them. They don't have an awful lot of options.")

He was asked standard questions for the master of any vessel: the Hamal's last port of call, its destination and to identify the crew. There were seven other men, aged between 26 and 63. Sahin provided passports for all those on board.

The National Deep Rummage Team on board their training vessel in Liverpool, October 2016 Greg White

The captain was advised that the vessel was now under the control of Border Force. The rest of the crew was moved to the mess by officers from the Valiant and informed that they were detained under the Criminal Justice (International Co-operation) Act, which authorised UK authorities to apprehend the crew in international waters.

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The vessel was then piloted westwards towards Aberdeen, a journey of around 14 hours. At 11pm on the night of the 23rd - 19km off the Scottish coast and therefore in UK territorial waters - Carruthers individually detained each of the crew members. Under Scottish law, this gave the authorities 12 hours to charge the men, although it was possible to obtain a 12-hour extension.



The custody clock was ticking.



The Hamal arrived in Aberdeen at around 1am on Friday 24, just over 14 hours after it had been boarded. During the passage to port a number of items had been recovered by Carruthers and others who had searched the wheelhouse and elsewhere. These included the ship's log and other documentation, a satellite phone, and a camera which was found in a cabin. "We were picking up documents, charts and equipment," Carruthers says. "But at that stage you don't know for sure the relevance of anything that you've lifted up."

In Gartcosh, some 200km to the south-west, McGowan was able to reflect on a successful coming together of a highly complex, international, multi-agency operation that had been conducted at extremely short notice. But, far from feeling satisfied, McGowan, who had been sleeping in the office, was feeling the pressure.



"My 24 hours were up at around 11pm on Friday. I had to charge them, or release them," McGowan says.



And there was one key element that had eluded the Border Force and NCA officers who had conducted the "surface search" of the vessel as it was brought into Aberdeen: they had yet to find any evidence of narcotics.

The Hamal was secured and the crew transferred to a police detention centre in Kittybrewster, Aberdeen. They were interviewed the following morning by NCA officers; some of the men chose not to respond to questions, others gave mixed responses. Ozmen made no mention of South America when asked about the route of the vessel. However, two of the interviewees informed investigators that they had been in Guyana.



"At no point did any of them admit any involvement with drugs, and indicated either that they were against drugs or genuine surprise - 'If you find any drugs, I'll be as surprised as you are,' that kind of thing," says Pauline Henderson, the procurator fiscal depute in the Scottish Crown Office. Sitting in a meeting room in Gartcosh, she speaks with the crisp expertise of her profession.



While they were being interviewed by NCA officers, the Turkish sailors were unaware that there was a new crew on board the Hamal: a group of elite Border Force investigators who had arrived in Aberdeen early that morning and are known to be world experts in finding contraband - guns, alcohol, pornography, cigarettes, narcotics and people - concealed on commercial vessels.



If anyone could find the cocaine, it would be the specialists of the National Deep Rummage Team (NDRT).

"What we're looking for is a needle in a haystack. We want to find this 35-metre ship - albeit it's bright red - somewhere out in the Atlantic Ocean" John McGowan, senior investigator at the National Crime Agency

The construction of seafaring vessels is a complex and high-stakes undertaking. Ships are subject to enormous forces; the fore-end - or front 25 per cent of a ship - absorbs a pounding that few man-made objects must endure, slamming into the waves on high seas that can routinely be more than six metres in height. All vessels must contend with constantly dynamic conditions: the area below the hull endures potent hydrodynamic forces which create a constant, rolling motion that challenges the ship's stability.

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In order for a vessel not to buckle at sea, it's built with a complex superstructure of pillars, girders, stiffeners, frames and metal plates that are welded together. The innards of the vessel - the large tanks needed for fuel, oil or ballast; the pump rooms and engine rooms; the so-called "peak tanks" that are necessary for stability; the boiler and up-take; store rooms and chambers for the steering gear; the chain locker for the anchor - are intricate and sometimes esoteric, even on a relatively small vessel like the Hamal. These are all sites a case of handguns or a bale of marijuana could be secreted and moved from one port to another, undetected in the vast network of the 50,000-plus commercial vessels that transport the world's goods from country to country.

The task of monitoring and securing maritime transportation is ever more testing because of the vast size of modern container ships. The largest, the 395-metre MSC Oscar, which was built by Daewoo in South Korea and began operating between China and northern Europe in January 2015, has a deck area equivalent to four football pitches laid end-to-end. The uncertainty of what lies below deck, allied to the porous nature of many ports, renders hidden, prohibited objects unknowable.

Consequently, specialist teams are required in order to conduct expert inspections for contraband. The NDRT is recognised as a global expert in surveying vessels, a task that is often conducted in extremely hazardous conditions. There are units based in Southampton, Felixstowe, Immingham and Liverpool - the last of which also serves as a training academy led by an amenable Liverpudlian named Paul Tunney, who oversaw the search of the Hamal.

The investigation began at 8.30am on the 24th, with the cutter crew working through the accommodation area while the Immingham-based NDRT team set to work in the engine room and the vessel's tanks. Tunney, 58, has a mop of grey hair and dark eyebrows. It's apparent that he relishes a 40-year career spent thwarting the activities of global smuggling gangs. But the process of the search that day felt different than usual to the members of the team.

Tunney and his deputy Colin Hill - a keen, trim man with grey hair and glasses who oversees the training of both the UK Deep Rummage team and those sent from France, Canada, Turkey and Australia, among others - describe their work as "like CSI in reverse", meaning that they are making a minute examination of a space in anticipation of it being a crime scene - rather than after an event has occurred. Usually they rely on experience and instincts (where a vessel is coming from, its route, how its crew behaves when boarded) to decide which ships to rummage in. It's unusual for them to be called by another authority and told that there is a strong probability of contraband being on board.

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Paul Tunney, head of the National Deep Rummage Team: "Having that clock ticking made life really hard" Greg White

"You're really looking for space - everything that's been built has space in it and that's where you're going to find a commodity," Tunney says. Once, ships remained in port for days, but today the turnaround is quick: sometimes a vessel will be docked for just a few hours. NDRT officers need to be able to make rapid assessments and strip down equipment and casings and reassemble them efficiently.



While the crew of the cutter searched the surface of the ship - the cabins, bridge and storage areas - the NDRT officers, aware that there were only three hours on the initial custody clock - started examining what Carruthers describes as "the guts of the vessel".

Lee Butler, then 31, was one of seven officers who had been detailed to search the forepeak store - the very point of the vessel, which is predominantly used, as its name suggests, for stowing items such as paint and rope - and the tanks. Often a search means officers putting themselves in danger. Members of Deep Rummage need to be able to move through the labyrinthine innards of a vessel, sometimes in darkness and wearing breathing equipment, looking for small clues.

There hasn't been a fatality in rummage since the 60s, a happy statistic that Tunney and Hill put down to training methods that were developed in the 80s. Typically, air contains around 21 per cent oxygen. A two per cent drop below this causes nausea, dizziness, loss of judgment and, eventually, unconsciousness; a two per cent increase, meanwhile, creates oxygen enrichment, which makes the atmosphere flammable.

Today, NDRT officers are only allowed to enter confined spaces with a self-rescue team as backup. They previously relied on the Fire Service for help, but this practice was imperfect - firefighters were often unable to get into the confined spaces that Rummage routinely operates in as officers had an oxygen cylinder on their backs.

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Rummage works differently - the breathing apparatus worn by its officers is supplied with air from a vehicle outside via an armoured cable which can support 900kg in weight that the officers pull behind them. It provides 50 hours of breathable air. If this fails, there are backup cylinders that last for 40 minutes, and a further fall-back - officers strap a small cylinder containing 13 minutes of air to their leg. For every officer inside a tank, three others act as support.

Usually on a ship, one or two of the tanks remain empty, yet those on the Hamal were full. One of them contained fresh water - yet Tunney had noticed supplies of bottled water elsewhere on the boat. The tanks were beneath the accommodation level, which was below the bridge. Entering the laundry room, towards the front of the Hamal, Butler and a colleague noticed chips of paint around the access area to the forepeak tank, a possible sign of disturbance.

They removed the nuts that secured the lid and peered inside. The tank looked full and smelled of diesel. The container was supposed to hold seawater - which is used as ballast while at sea - but not usually at the level at which it appeared to be that afternoon in Aberdeen. Butler, who had inspected hundreds of tanks, was aware that contaminating water with oil or diesel could have been done to prevent a close inspection. In order to search the tank it would have to be emptied. And the adulterated liquid couldn't be pumped straight out into the harbour - they needed to transfer it to another container, which would cause further delays.

"Having that clock ticking made life hard," Tunney says. "Really hard."

At 11am on Friday the initial 12-hour period was extended to 24 hours by a police inspector on the basis that the investigation merited more time. McGowan was scrambling to find a receiving tanker for the contaminated liquid. Twelve hours later, the crew of the Hamal would need to be charged or could walk free. "We had a very fraught Friday afternoon," Carruthers says.

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"My 24 hours were up at around 11pm on Friday. I had to charge them, or release them" John McGowan, senior investigator at the National Crime Agency

A road tanker arrived at around 7.30pm and the team began to drain the forepeak tank. Once that was done, "mini gases" were lowered into the container to test the atmosphere. The alarms are standard issue for the officers and must be worn at all times. Confined spaces are the most likely repositories of toxic air, but any unventilated area could cause danger. "The alarm covers oxygen, methane, H2S [hydrogen sulphide], carbon monoxide and we have another one for fumigants, because some of the hulls get fumigated to stop bugs and snakes," Tunney says.

Wearing breathing equipment, Butler climbed into the tank to make a visual inspection at 9.20pm. The walls of the tank were corroded and rusty; the chamber was just about large enough for two men. He moved his torch around in the gloom, searching for anything unusual. His curiosity was piqued by a number of pipes that had been cut, and there was a baffle, a strengthening plate with holes large enough for a person to pass through.

It separated the tank into two sections that ran from the pointed part at the front of the Hamal to the bulkhead. The walls were uniformly red in colour but, as the beam of the torch crossed from one side to the other, the officer noticed a slightly different shade. He looked more closely, trying to make out what it was he was looking at: a metal plate measuring around 50cm by 30cm had been welded facing rearward into the bulkhead on the starboard side of the vessel.



The boat's plans were examined, but were inconclusive. There are many reasons why a plate might have been welded there, but the only way of eliminating the container as a concealment was to find out what was behind it. Officers were concerned that there may be fuel on the other side, so using cutting gear - which would generate sparks - was deemed too dangerous.

By this time there were just a few minutes left on the custody clock. Butler climbed back into the tank with a drill and placed the bit against the steel plate. As it rotated, it sunk into the surface, shavings dropping to the bottom. The officer suddenly felt a release in pressure - the bit was on the other side. There were no sparks, no explosion.



Butler withdrew the drill. He looked at the end of the bit and saw white powder. The tool was passed to colleagues on deck who conducted a "presumptive test" of the substance - analysis conducted in the field before samples are sent to a laboratory for conclusive procedures. A sample of the white powder from the drill bit was placed in one of the cartridges used for testing. A solid line formed alongside that of the control line in the tube: it was positive for cocaine.



It was 11.20pm on Friday 24. The custody clock had just timed out.

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The drill - with white powder stuck on the bit - used to pierce the Hamal's forepeak tank NCA

The interviews with the crew of the Hamal had concluded by the time the news of the discovery of the cocaine came through, but the crew had yet to be released from custody. As the Turks had all been detained individually while at sea, they had different start and finish times to their detention, meaning that some had timed out before being charged, but were detained under the Immigration Act as they had not been cleared by Border Force to enter the UK.

Any hopes Sahin and the others were harbouring about being released were extinguished at 1.29am on the 25th when the first of the crew was cautioned and charged. Processing all nine of the men took two-and-a-half hours. They were accused of smuggling cocaine and being concerned with its supply.

Deep Rummage returned at 8.00am the following day with a distinct mission: they might have discovered cocaine on the Hamal, but it was unclear exactly how the narcotics had got there and how much of it there was on board. Specialist cutting equipment was required to puncture the thick steel walls of the tank. The Aberdeen Fire and Rescue Service was brought on board: its officers had the necessary tools, but weren't able to work inside the container.

Space was tight and fire service oxygen tanks only last for 40 minutes. Rummage officers would be able to work for longer because of the continuous air supply from their support vehicle, which was parked on the quayside. It was decided that Butler and his colleague Mark Feasey, 55, would take the Fire Service equipment and cut the panel. They entered that tank at around 9.50am, initially drilling holes to aid the electric saw. Conditions were cramped and the saw's blades kept breaking; a horizontal cut was made, before incisions on the left and right hand side of the plating.

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"You couldn't do it with a [blow] torch because there's a chance of damaging what was on the other side and it was such a tight space," Tunney says. "So they went in and were cutting away, going through blade after blade."



After more than three hours of cutting, with plumes of cocaine now swirling around them where the saw had sliced through to the other side, it was decided that the metal plate had been pulled back enough to try using a Kevlar air bag - employed by the Fire Service to lift vehicles from victims - to force it back further. The air bag burst.



Throughout the afternoon of the 25th, the two Rummage officers worked centimetre-by-centimetre to create an incision large enough to access the cocaine in the void behind the tank. At around 9pm, after 12 hours of cutting and prising, Butler and Feasey had a view of what was beyond the plate: bales wrapped in white plastic.

"You're really looking for space - everything that's been built has space in it and that's where you're going to find a commodity" Paul Tunney, head of National Deep Rummage Team

The officers returned the following morning, Sunday 26, and continued to work. Space was tight and the men had had little rest but, at around 1pm, they finally removed the metal plate. Before them were four white bales that were tightly packed together. The packages were so close-fitting that getting purchase in order to pull them out was fiendishly hard. Butler, Feasey and another officer alternated trying to prise one of the bales from the stack, ultimately realising that they needed to break it apart in order to create enough room to get a grip on others. Once the first was removed and placed in an evidence bag, 11 other bales were painstakingly pulled from the hatch. The process was frustratingly slow.



"It was on the Sunday that they said, 'Look, something's wrong here, it couldn't have come in that way - it had to come in another way,'" Tunney says of the bales. "The same team decided then to find out from the plans what was above that tank." The layout on the accommodation level included cabins. In one, number seven, there was a large, upright medical cabinet. "One of the female officers noticed that the carpet was slightly missing and she could see a small bit of cement," Tunney says.



At around 9pm that night, the cabinet was pulled to one side, revealing an area beneath that appeared to have been inexpertly but recently concreted. Using a hammer, the team chipped away at the grey surface of the covering; the officers were able to see the outline of another lid, which had been sealed with mastic, and an oval-shaped access area just larger than shoulder width.

Prizing open the covering, officers shone a torch into the darkness: there was a cavity not much wider than the entry point that ran laterally across the boat. Inside, tightly bound in white plastic secured with black ties, were multiple bales of cocaine stacked in two rows.

Butler and Feasey climbed into the tank using a rusty ladder, which was the only permanent access into the area. Their task was then to haul the bales of cocaine from the cramped space with the help of a rope and pulley. By around lunchtime on April 28 there were 128 bales stacked in plastic forensic bags on the quayside that had been lifted in a cargo net by a crane. The packages were later revealed to weigh 25kg each.



"We had to put the same two guys who'd been in the tank for two days in the hull for evidential purposes," Tunney says. "They were under breathing apparatus for 29 hours."

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Under a cabinet in a cabin was a patch of freshly laid concrete. Beneath that was a narrow, oval-shaped access panel. Under that: 128 bales of cocaine NCA

DC Jurgen Wahla, then 42, from the Organised Crime and Counter Terrorism unit, based in Portlethen, south of Aberdeen, was part of the team that prepared a report into the value of the drugs recovered from the Hamal. He appeared as a witness for the Crown during the trial, which started on April 20, 2016, and ran for 12 weeks.



Forty-one of the 3,200 packages inside the bales - each weighing approximately a kilogram - were subjected to forensic analysis, which revealed a purity that ranged from 58 to 74 per cent. Wahla puts this inconsistency down to the haphazard "bucket chemistry" of the organised crime groups who manufacture it in less-than-optimal conditions in the jungles of South America. Wahla estimated that, once it was sub-divided into one-gram deals, "It would have the potential to realise £512 million."



It took three days to remove all of the bales. If it hadn't dawned on them already, the Border Force, NCA and other agency officers working on the case could then form a clear picture of what had been on the Hamal: the tugboat had been carrying a volume of cocaine slightly less than the entire quantity of class-A drugs that were seized in England and Wales throughout the whole of 2014. It was the largest seizure in UK history.

"MV Hamal’s 3,200-kilogram cargo of cocaine has a street value of £512 million"

"You must never confuse the really large amount of drugs on a boat with overwhelming evidence," says procurator fiscal depute Pauline Henderson one overcast August morning, sitting in a conference room at Gartcosh. "Because the crucial point for the Crown to prove is knowledge… If a routine inspection had just gone on and walked through that boat, there's nothing to indicate that there's 3.2 tonnes of cocaine on it. And if that's true for anybody walking through the boat, it's also true for the crew until you prove that it's not true for the crew."



The nine men on board the Hamal all claimed to be innocent. On May 11, 2015, Henderson was allocated the case to build a narrative of the evidence and make a recommendation as to charges. The team spent weeks scrutinising the evidence that had been taken from the Hamal, including paperwork, logs, notebooks and a camera. Arguably the most crucial piece of evidence, the ship's laptop, was analysed by a maritime data specialist.

"The navigation software is the full journey that was recorded," Henderson says. "The accused probably didn't know it was recording it, as it was an automated function of the laptop. It took its own position every hour that the laptop was switched on. So we had 14,000 plot positions. They did know that they had plotted certain waypoints for the journey, so we had waypoints from Tenerife up around the coast of Scotland, and to the final point that we believe was their intended destination."

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The Hamal had weighed anchor on February 22, 2015, in Tuzla, a municipality in Istanbul, and informed the harbour master that it was to progress from Istanbul to Albania. The tug passed through the Dardanelles and into the Aegean; but instead of setting course for Albania, the boat headed west through the Mediterranean, exiting into the Atlantic through the Straits of Gibraltar, and charted a course to Tenerife, where it refuelled on March 8. The journey from Istanbul had taken two weeks. It took a similar amount of time to reach its next destination - Guyana, where it docked in the capital, Georgetown, on March 21.



Pirates occasionally target vessels moored in Georgetown, so boats are guarded by security personnel. The company contracted to protect the Hamal had been told that it would be in Georgetown for ten days. Five days later, the tug left unexpectedly and made its way back across the Atlantic.



After leaving port, the vessel steamed eastwards for 36 hours at a speed of around ten knots, before maintaining its position in the roiling ocean. The boat zig-zagged, as if it was under steam at some points and drifting with the tide during others. After a couple of days, it headed eastwards back to Tenerife.

Over the following days, the Hamal headed north up the west coast of Ireland towards the north of Scotland. On Monday April 20 at 8.57am, it received an email containing some co-ordinates. "Good morning," it read, "the meeting is 87833058. Please inform us about your estimated arrival."



A response was sent at 10.33am the same day: "Have a good day. It might be 24/04 at around 22:00. Greetings."



At 9.30am on the 21st, the Hamal continued to steam north from its position 200km west of the island of Barra in the Outer Hebrides. Two months into its journey, the tug reached Pentland Firth, which separates the Orkney Islands from Caithness on the mainland, one of the busiest areas for shipping in the UK. The co-ordinates it had received on the 20th had directed it to a rendezvous west of the German island of Sylt, close to the border with Denmark.

A Deep Rummage officer is lowered into a ship's tank on a training drill Greg White

On the 23rd, a further email was sent from the Hamal, which had by then passed over the top of Scotland and was progressing in a south-easterly direction. "Have a good day," the message, time-stamped at 10.05am, read. "Shall we make arrangements at ETA 17:00? Or shall we continue in this way. We are in the position to open the device. Shall we open it now." An hour later it was boarded by UK authorities.



The Crown based its case on the understanding that it is unlikely that the narcotics were on the Hamal when it left Istanbul in February the year before.



"Cocaine doesn't come from anywhere other than South America," Henderson says. "It makes no sense to send your half-a-billion-pound cargo into the sea, to send it round the world back to where it came from."

Both the deck log and engine log registered that the vessel had sailed from Tenerife in March and had dropped anchor in Dakar for approximately three weeks before sailing back to Tenerife. The deck log was signed off daily at the foot of every page by the captain.



"The engine log had a similar false record of the journey, and that's fully completed by the chief engineer," Henderson says. "Then we had another log which was to do with the running of the engine. This was indicative of the true journey because it showed the engines running all the time the vessel is travelling to Guyana, and it showed them being off for the five days they were in Georgetown. We have Sahin and Ozmen completing a log indicating they're in one place, and we have photos of them in a bar in Guyana on the days they said they were off the coast of Dakar."



The Crown's position was that the crew signed false logs because they were in Georgetown waiting to be given the details of the rendezvous to collect the drugs, and that it's likely that the period the boat spent zig-zagging for two days off the coast of Guyana was where the bales of cocaine were loaded. Henderson characterises the movement of the boat as "a very definite pattern that doesn't match tidal patterns."

Captain Mumin Sahin (left) and second captain Emin Ozmen (right) received 22-year and 20-year sentences respectively NCA

As for the rest of the crew, the Crown relied on "baseline evidence": the size of the boat; the width of the corridors; the size of the concealment and the number of bales; the fact that the size of the bales means that only one package could pass along the corridor at any time; the location of the cabins where the crew slept; the route that needed to be taken to move the drugs through the vessel; and the location of the entrance of the concealment.



"By implication, 128 bales came one at a time through this corridor," Henderson says. "If you were on that boat, you saw it happen."



Investigators recovered 22 emails in Turkish from a satellite phone. Two separate email addresses - a Yahoo! and a Gmail account - were used; both indicated that they were from an entity called Kiev Shipping.

Henderson deduced that the eight-digit number - 87833058 - sent on April 20 was, in fact, co-ordinates that had been altered using a rudimentary code, involving subtracting three numbers. Notes found on the boat showed that conversion to longitude and latitude being made on paper. It matched the co-ordinates of a marking on a chart that was found on the vessel; a plot position with a circle and a cross through it, just off the coast of Germany.



The method of concealing the co-ordinates was "a ridiculously simple-minded code," according to Toby Bailey, a mathematics professor at Edinburgh University who appeared at the trial as an expert witness. "The whole situation would be understood in a couple of minutes by a bright 12-year-old."


Hamal's route from February 22 to April 22, 2015, including five nights in Georgetown, Guyana WIRED

On a brisk, chilly morning in mid-August, in Glasgow's High Court of the Judiciary, a sandstone edifice with colonnades not far from the River Clyde, Sahin and Ozmen, both of whom maintain their innocence, were sentenced by the Honourable Lord Kinclaven. The convicted men were brought into the courtroom between two guards and listened gravely to the interpreters as the judge read the social-work reports that had been prepared about the two men. Kinclaven noted that neither had previous convictions and were "not at the top of the drugs hierarchy", before adjourning the court to consider the sentences. At 10.11am he re-entered the wood-panelled courtroom. Sahin sat contemplating the verdict sombrely: he received two 22-year sentences, which are to be served concurrently. Ozmen raised his head and stared directly at the judge. He will serve 20 years. The men were handcuffed and led to the cells below.



According to McGowan, Kiev Shipping, the registered owner of the Hamal, is "a brass plate company in the Marshall Islands in the Pacific." The investigator isn't convinced that it even exists, pointing out that any legitimate trading company that had one of its vessels seized by the authorities would have immediately despatched lawyers to repossess it. "We're deafened by the silence," McGowan says. "Nobody contacted us, there's been no one coming forward saying 'that's my ship'."

The Hamal is being stored at an undisclosed location until the defence and Crown agree that it is no longer required as part of any appeal that the convicted men might bring, then it will be disposed of by the Border Force. The panel that Butler drilled through turned out to have been a repair undertaken by the previous owners of the vessel.



The other seven Hamal crew members have been repatriated to Turkey. Three men were acquitted during the 12-week trial; the jury returned verdicts of not proven on four others.



"Various other crew at interview gave explanations as to how they got the job," Henderson says. "One said he met somebody in a casino, another said he saw an advert at the bus stop. The consistent position was that a man by the name of Ahmet Kurtulus gave them their job, and that he was some form of shipping broker. But that person, beyond their name and their details being in a lot of correspondence, was never identified."