Trident-carrying subs are coming to Plymouth

Training is now underway to ensure staff are prepared for the next exercise in May.

The MoD made the admission on Thursday.

It came on the same day as news that a redundant nuclear submarine, HMS Courageous, is to go on public display at the base, partly to reassure the public over safety.

The test result has worried campaigners monitoring the base, which is due to begin refitting submarines armed with Trident missiles from next year.

Campaigner Stuart Parfitt said: "If you have an accident, you can't go back and say, 'Let's do it again.'

Public confidence

"There are no second chances.

"I hope that they get it right when it counts."

The base commander, Commodore Ric Cheadle, said: "I hope that public confidence isn't dented.

Visitors will be able to tour HMS Courageous

"We run these exercises because we are keen to be on top of these situations.

"If we didn't exercise, then we wouldn't find out how we could improve.

"We're also keen to make the results of those exercises public."

Exercise Kismet was a joint operation between the MoD and the dockyard operating company, DML.

Commodore Ric Cheadle said putting HMS Couragous was part of a move to open up the base to the public.

He said: "We want to take the mystery out of how a nuclear-powered submarine works, and let the public see for themselves how safe they are and to learn about how we maintain and operate them."