The Royal Fleet Auxiliary (RFA) has helped seize more than £35 million worth of drugs in the Caribbean.
Working with the United States Coastguard and law enforcement, 1,400kg (1.4 tonnes) of cocaine was confiscated.
A further 150kg of cocaine worth £3.75 million was ditched in the sea.
On board Mounts Bay was a MH65 helicopter, which was on patrol when what was described as a 'go fast' craft was spotted.
The 'go fast' boat was then intercepted by the RFA vessel, and US Coastguard personnel then sent to stop the craft and seize its cargo.
Mounts Bay's commanding officer, Captain Kevin Rimell, said his crew should "feel proud" about their role in the drug bust.
Armed Forces Minister, Anne-Marie Trevelyan said: "Thanks to the work of the Royal Navy and our US partners these narcotics will not reach the streets and fuel further criminality.
"RFA Mounts Bay has had a varied deployment, from leading the response to Hurricane Dorian to stopping the illicit drugs trade.
"This is a timely reminder of the diverse work undertaken by our Armed Forces that helps keep up safe."
"These interdictions highlight the importance of working with our allied partners such as the United Kingdom Royal Navy," said Rear Admiral Eric Jones, Commander of the Coast Guard Seventh District.
A.J. Collazo, the special agent in charge of the Drug Enforcement Administration's Caribbean Division, said these operations "reiterate the significance of intelligence and resource sharing".
The Royal Fleet Auxiliary is the Navy's uniformed civilian support branch, providing operational support.
Staffed by merchant sailors, RFA vessels such as Mounts Bay are involved in warfighting, counter-narcotics, law enforcement, disaster relief and evacuation.
Last year, RFA Mounts Bay completed a ten-day aid mission in the Bahamas following Hurricane Dorian, highlighting the RFA's support to those inside and outside of the military.
Cover image: Some of the drugs seized during the operation (Picture: Royal Navy).