Drug smugglers began throwing their illicit cargo overboard after spotting Royal Marines approaching.

HMS Medway was one of two Royal Navy vessels that helped seize an estimated £166 million of drugs in a joint operation with US forces.

The crew of the River-class offshore patrol ship - commissioned in Chatham last year - worked with an onboard detachment of US Coast Guard Law Enforcement officials, intercepting two vessels in the Caribbean Sea, and seizing 1,433 pounds (650 kilos) of cocaine.

The British naval vessel RFA Argus also seized 789 (358 kilos) pounds of cocaine in another of 12 interceptions carried out by British ships, US Coast Guard and US Navy vessels between August 27 and September 8.

The Royal Navy task says the cocaine seized by the British vessels would be worth £81m on Britain’s streets.

In total 12,100 pounds (5488 kilos) of cocaine and approximately 5,759 pounds (2612 kilos) of marijuana was seized and offloaded by the Coast Guard Cutter Harriet Lane in Port Everglades, yesterday.

In the first success, an American maritime patrol aircraft spotted a suspicious vessel riding low in the water and reported it to Argus, which immediately changed course to investigate.

The 28,000-tonne vessel used stormy weather as cover to stay out of sight and avoid raising suspicion – while her boarding team of Royal Marines of 47 Commando and the US Coast Guard prepared to strike.

On approaching the target craft, the Royal Marines were spotted and the suspect vessel’s crew started to throw their illegal cargo overboard.

Coxswain Corporal Max Bygraves, of 47 Commando’s 539 Raiding Squadron, said: “Some patches of heavy rain had hidden Argus from sight in the distance and we were closing in unseen. When we were one mile off they saw us and started to run for it. We gave chase.

“We could see people on board throwing packages into the sea. This is important evidence, so we had to stop and collect one. The rest were picked up later. We then continued the chase and managed to catch the vessel.

“I am really pleased that all the hard work paid off. It was a team effort, and I am particularly proud of my team for the long hours they put in on the water.”

The crew of the intercepted vessel were brought back to RFA Argus along with their seized cargo before being transferred to US Coast Guard cutter Spencer.

Their boat was subsequently sunk by soldiers from 24 Commando Royal Engineers.

A few days later, offshore patrol ship Medway acted on reports of a suspicious go-fast, diverting course and launching sea boats piloted by Royal Navy sailors with a US Coast Guard Law Enforcement Detachment aboard.

Sixteen bales of cocaine and three detainees were captured in the first boarding, which saw Medway catch up with the suspect craft from 45 miles out.

Just one day later more information was fed to Medway and she gave chase to another craft, landing a further nine bales and three more detainees.

Those detainees and the seized drugs have now been handed over to US authorities allowing Medway to resume patrols of the region.

RFA Argus and Medway are deployed to the Caribbean as part of a Royal Navy task group.

They are in the region to support island communities during hurricane season, but also to carry out maritime security and counter-narcotics operations in collaboration with the UK National Crime Agency.

The UK also works in partnership with allied nations in the region as part of the Joint Interagency Task Force South, which detects and monitors activity to support security operations from their base in Florida.

Commanding Officer of HMS Medway, Lieutenant Commander Jim Blythe, said: “The Royal Navy and the US Coast Guard have prevented a significant quantity of drugs crossing the Caribbean that could have been destined for the streets of the UK.

“It is testament to my ship’s company, along with the US Coast Guard, that we have captured such a large amount of drugs and smugglers in such a short space of time.

“They have done themselves, their families and the country proud. This marks the start of what will hopefully be many interdiction operations as we continue to operate in the Caribbean.”

The US coastguard said it "strives for close coordination between partnering naval assets as well as its own" and that effective communication, persistence and teamwork contributed to the mission's success.

The Coast Guard remains committed to increasing counter-narcotic operations at sea, to "diminish transnational threats and maximize our country’s security."

Capt. Dorothy Hernaez, commanding officer of the Cutter Harriet Lane, said: "This large amount of drugs was seized in just a short 13-day span, shows just how serious the issue is.

“I am very proud of the efforts by not only the Harriet Lane crew, but also all the other Coast Guard, Navy, and British Royal navy assets involved in the interdictions. These crews overcame significant challenges related to COVID-19 to remain both operational and effective, in order to keep these drugs off our streets."

U.S. Southern Command began enhanced counter-narcotics operations in the Western Hemisphere on April 1, to disrupt the flow of drugs in support of "Presidential National Security Objectives."

Read more: all the latest news from Medway .