The captain and first officer of an ocean going tug have been found guilty of drug trafficking in what authorities have described as the biggest seizure of class A drugs ever in the history of the United Kingdom.

The cocaine was found hidden on board the Tanzanian-flagged MV Hamal in April 2015.

The vessel was intercepted by Royal Navy and Border Control assets in the North Sea about 100 miles off the coast of Aberdeenshire following a tip from the UK’s National Crime Agency working with French customs investigators. The MV Hamal was later escorted to the Port of Aberdeen where an exhaustive search turned up 128 bales of uncut cocaine stashed inside a hidden compartment next to one of the tug’s ballast tanks.

The total weight of the cocaine taken off the MV Hamal turned out to be in excess of 3.2 tonnes, worth an estimated total street value of the drugs to be about £512 million.

Hamal’s nine crew members, all Turkish nationals, were detained and charged with drug related offenses.

Investigators later determined that the ship likely loaded the drugs at sea about five days after leaving the Georgetown, Guyana off South America’s North Atlantic Coast in March 2015, and were destined to be offloaded in North Sea, north of the Dutch/German border.

Of the nine crew members detained, charges against four were found not proven and three others were acquitted, however a 12 week trial at the High Court in Glasgow found the captain, Mumin Sahin, and first officer, Emin Ozmen, guilty of two counts of drug trafficking. Sentencing has been set for August 12.

“This seizure was unprecedented in scale, the biggest ever class A haul in the UK, and we believe the biggest ever maritime seizure of cocaine in Europe,” commented NCA senior investigating officer John McGowan. “While we suspect that the end destination for this load would have initially been mainland Europe, there is no doubt given the size of the seizure that a good percentage would have ended up being sold in the UK and fueling further criminality.”

“Our investigation has been truly international and we have relied on support of law enforcement colleagues across the globe, including France, Turkey, Guyana and Tanzania,” McGowan.