The Royal Navy is investigating reports that a nuclear submarine crew held a party after returning to their UK base while the rest of the country was under coronavirus lockdown.

Social media footage has emerged of the crew of the HMS Trenchant apparently enjoying the barbecue and party after returning to base at Devonport, Plymouth.

The 30-second clip shows two sailors standing behind a makeshift DJ booth covered with a sheet with “HMS Trenchant Prison Party” written on it.

They are playing dance music while some of the crew stand watching and others sit at wooden benches on the quayside.

It is understood the party took place earlier this month while the rest of the UK was in lockdown, after social distancing guidelines were introduced because of Covid-19 pandemic.

The Times reported that the captain of the submarine has been placed under “administrative investigation” over concerns about his judgment in allowing sailors to host a party to celebrate coming ashore when the rest of the country was in lockdown.

The submarine had returned to Devon after being on manoeuvres for several weeks.

The newspaper reported the crew were remaining in quarantine together onboard before deploying again.

It was also reported that two lower-ranking seamen were disciplined for refusing to comply with an order from a senior naval base officer who told them to end the party.

Just off patrol and they can’t go home. I know where most sympathy is going to lie

A former naval officer told The Times: “This really comes down to the nature of the order to not do it. If it was ‘you will not’ then that’s one thing. If it was more of a ‘do you think this is a good idea’ then that’s another.

“But he’s been in a cramped submarine, just off patrol and they can’t go home. I know where most sympathy is going to lie.”

HMS Trenchant is a Trafalgar-class submarine equipped with the Tomahawk cruise missile, which can destroy a target from up to 1,000 miles away.

A Royal Navy spokesman said: “An investigation is under way. It would be inappropriate to comment further.”