The pair were both ordered to pay �146 compensation

Plymouth Magistrates' Court heard on Friday they cut through the fence before scrambling on board HMS Vanguard at Devonport Naval Base.

Petter Joelsen, 22, a Swedish national of Dalmarnock Road, Glasgow, and 19-year-old Elisa Silvennoinen, from Finland, were conditionally discharged for 12 months and six months respectively, but pledged to continue their protests.

District Judge Barbara Barnes ordered them to pay �146 each in compensation.

After the hearing Mr Joelsen said he was disappointed at being convicted.

Tea and biscuits

"We do not believe we committed a crime," he said.

He and Ms Silvennoinen, an environment student, said they would be taking part in a protest at Faslane naval base in Scotland next month.

The pair, who denied criminal damage, told the court on Thursday they spent up to 30 minutes on the vessel, which was in dry dock at Devonport Naval base, and even spent some minutes inside the conning tower.

Then they set off fire alarms to draw attention to themselves on the vessel.

They were given tea and biscuits by Royal Navy security personnel who caught them.

Huge embarrassment

A member of the UK anti-nuclear group Trident Ploughshares, Mr Joelsen said he and his co-defendant were acting as weapons inspectors.

South East Cornwall Liberal Democrat MP Colin Breed said the protesters had done a favour by testing the security at the base.

He said what happened was a "huge embarrassment" for the dockyard and the Navy and he felt the conditional discharges were appropriate.

A Royal Navy spokesman said on Friday that security at the base had been tightened since the incident.