The future king was serving in the Portsmouth-based frigate HMS Iron Duke when it intercepted a boat hundreds of miles off the coast of Barbados on Saturday.

The huge stash of cocaine was seized in a joint operation with the US Coast Guard just after midday local time, about 5pm here.

It is thought the 50ft power boat was carrying the illicit cargo to be sold on the streets of Europe or West Africa before it was detected by the ship's Lynx helicopter.

United States Coast Guard personnel on board Iron Duke then boarded the boat and discovered 45 bales of cocaine, weighing 900kg - almost one ton.

It was seized and transferred to HMS Iron Duke, and the boat's crew of five men were arrested.

The boat turned out to be in very poor condition and actually sank later.

The Ministry of Defence had not revealed details of Prince William's involvement this morning, but have confirmed he was onboard Iron Duke when the daring raid happened.

Commanding Officer Commander Mark Newland said: 'This is a fantastic start to HMS Iron Duke's North Atlantic Deployment.

'To have had a direct impact on the flow of cocaine into Europe just four days after we arrived in theatre shows the benefit the Royal Navy can have in the area of maritime security and counter drug operations.

'From the first moment the Lynx helicopter discovered the suspect vessel, my ship's company, working hand in glove with our US Coast Guard colleagues, turned this opportunity into a certainty and ultimately a successful seizure.

'I am immensely proud of all their efforts.'

The Serious Organised Crime Agency, in association with the British-led Maritime Analysis and Operation Centre in Lisbon, worked together to bring about the raid.

Prince William had only been in Iron Duke for a few days after completing his training in Portsmouth and at Dartmouth.

He will be with the ship until August 1 as it completes its North Atlantic patrol duties.

Her primary role is to provide a UK presence in the region and support British Overseas Territories.