The man behind the audio of Iran's seizure of a British-flagged tanker in the Gulf said shipping firms are preparing to ditch the UK-ensign in favour of China to avoid the wrath of Iran.

Phil Diacon, head of Dryad Global, a London-based shipping risk management company, spoke after the dramatic hijacking of the Stena Impero in the Strait of Hormuz on Friday.

Phil Diacon, head of Dryad Global, a London-based shipping risk management company, said major shipping firms were looking to shift to China-flagged vessels after Friday's dramatic hijacking

He said his global clients - major shipping firms - were starting to look at alternatives to using British-flagged vessels in the Gulf because the Iranians had 'no interest' in disrupting the shipping of other nations.

The man behind the audio of Iran's seizure of a British-flagged tanker in the Gulf said shipping firms are preparing to ditch the UK-ensign in favour of China to avoid the wrath of Iran. Above: The Stena Impero at the heavily guarded Iranian port of Bandar Abbas

'Normally it's the British-flagged, US-flagged and Saudi-interest vessels that are the most likely to be targeted,' Diacon said.

What does it mean for a ship to sail under a country's flag? While the Stena Impero is a British-flagged vessel, it is owned by Swedish shipping firm Stena AB - which is headquartered in Glasgow. Being 'British-flagged' means the vessel is registered in the UK and is covered by the maritime laws of that country. A vessel does not have to have any physical connection to the country in which it is registered and merely has to have an application accepted by that country's shipping authorities. A ship can only fly one flag at a time, but can change flags at any point. As a result, some owners seek a so-called 'flag of convenience' which they believe will offer benefits. Panama and the Marshall Islands are well-known for offering easy registrations and other benefits for those registering there, in the hopes of attracting business. As a result, Panama has the largest ship register in the world, with the Marshall Islands second in the 2018 list. Advertisement

He said it takes at least a month for shippers to complete the paperwork needed to have their vessels registered under a different national flag.

He said most were now looking to China - a major player in the Gulf region that Iran views as an important ally.

'We are starting to see talk of moving to Chinese-flagged vessels,' said Diacon.

'Oil will continue to flow. The Iranians have no interests in disrupting other nations.'

Being 'British-flagged' means the Stena Impero is registered in the UK and is covered by its maritime laws.

Almost a fifth of the world's oil passes through the 21-mile (33-kilometre) strait between Iran to the north and the United Arab Emirates to the south.

Diacon refused to discuss how he obtained the audio of Friday's high-seas drama over the Stena Impero.

But he said the entire exchange was conducted over an open channel - number 16 - which is used globally by military and commercial vessels to send out calls.

Britain's helplessness in the situation has seen Foreign Secretary Jeremy Hunt get accused of devoting too much time to his ongoing UK leadership bid and not enough to his diplomatic duties.

Diacon agreed that 'this obviously did, to an extent, catch the UK by surprise'.

'The shipping industry was not really prepared for this.'

Iran seized the vessel weeks after Britain detained an Iranian vessel off the coast of Gibraltar.

They claimed the US ordered the British operation amid a standoff between the two countries, but the UK claims the tanker was violating EU sanctions.

Phil Diacon said his global clients were starting to look at alternatives to using British-flagged vessels in the Gulf because the Iranians had 'no interest' in disrupting the shipping of other nations

Today Iran released Tehran released video of some of the 23-strong crew of the Stena Impero sitting around a table speaking with one of their captors, alongside fresh images showing Revolutionary Guardsmen on board the Swedish-owned vessel.

The video shows seven of the crew wearing red jumpsuits and sitting around a table, as one Iranian guard can be heard thanking them for their cooperation.

The cameraman can also be heard telling them not to look at him.

Another video shows the crew laughing while standing around a coffee machine, and the ship's cooks preparing food in an apparent attempt to show they are being treated well.

Pictures released by the semi-official Fars news agency earlier in the day show some of the crew - which includes 18 Indians, three Russians a Latvian and a Filipino - huddled cross-legged on the floor.

Keeping watch: An Iranian Revolutionary Guard patrol boat sails in front of the Stena Impero, the UK-flagged vessel which was seized by Iranian authorities on Friday

Standing over them in a Revolutionary Guardsman, while items of bedding and towels are scattered around the room.

Their shoes have been taken off and piled in a corner. Two others photos show an armed guardsman on the deck of the tanker, and the tanker being watched over by armed boats at the port of Bandar Abbas, where it is being held.

The photos and videos are Iran's latest taunt to Britain, after it also released video of its flag being raised over the vessel and the Islamic call to prayer being played through its speakers.