A Royal Navy frigate on patrol in the Caribbean has helped block more than three tons of drugs which were thought to be destined for Europe.

Type 23 frigate HMS Iron Duke has been on Atlantic Patrol Tasking (North), which sees her operating in both the Caribbean and off the west coast of Africa – earlier in the deployment she was required to dash eastwards across the Atlantic to show the White Ensign in Sierra Leone.

Now back on the western side of the ocean, Iron Duke was alerted by British Customs and Excise officials and intercepted a Panamanian-registered merchant ship some 400 miles off St Lucia, using her Lynx helicopter during the operation.

The frigate put a team of US Coast Guard law enforcement officers on board the mv Yalta, and a team of Royal Navy personnel helped the Americans make a thorough search of the 11,450-ton ship.

During the search, more than three tons of cocaine was discovered – valued at more than £250 million - hidden behind false bulkheads and decking, and the American team arrested the 17-man crew of the Yalta, believed to be from Estonia, Lithuania and Estonia.

The search of the ship was continuing in the hope of finding more contraband.

The seizure of the Yalta continues a run of successes by Iron Duke. Last month, she helped track and chase two ‘go-fast’ speedboats in the Caribbean in the space of three days.

In the first incident, the suspected smugglers were seen jettisoning cargo over the side as they fled from the frigate, and in the second the speedboat was beached and the crew picked up by local law enforcement officers – along with 200kg of cocaine.

At the beginning of May Type 22 frigate HMS Cumberland made a fast passage 1,500 miles into the middle of the Atlantic from Devonport to help Spanish and British Customs officers intercept a converted German Jaguar-class Fast Attack Craft which was found to be carrying 3.5 tons of cocaine en route to Europe.

That operation was supported by the new RFA tanker Wave Knight and helicopters of the Fleet Air Arm.