Anti-nuclear protesters who had occupied an island near Britain's largest naval yard in Plymouth have started their blockade of the base.
The protesters were served with an eviction notice on Wednesday
Police arrested one person for obstruction on Friday morning at Devonport Dockyard where Trident nuclear submarines are refitted.
The protesters were evicted from privately-owned Drake's Island in Plymouth Sound on Thursday.
Friday's action is part of a weekend-long peace camp in the city.
The action is being taken by the Campaign for Nuclear Disarmament (CND) and Trident Ploughshares.
CND chairwoman Kate Hudson will be in Plymouth urging the ending of the refit programme and for the UK's Trident nuclear weapons system to be scrapped and not replaced.
The protest is taking place exactly a week after Trident Ploughshares supporters occupied privately-owned Drake's Island in Plymouth Sound.
Trident nuclear submarines are refitted at the base
A district judge ordered the squatters to vacate the island - which they declared a nuclear-free state - by 1545 BST on Thursday.
A spokesman for the group said it had left the island to set up the new camp on the mainland.
Devonport is the base for refits of the Royal Navy's Vanguard class nuclear-powered submarines, which are each capable of firing 16 Trident missiles with nuclear warheads.
Police said the person arrested was a 60-year-old woman from Essex.