Polaris submarines could have been West-based

Nuclear-powered Trafalgar-class vessels are already refitted within sight of homes on the Cornish side of the River Tamar.

Commodore Ric Cheadle, Devonport's current naval base commander, says great changes since the 60s mean safety is not compromised at the base.

Its refit operations have been limited after it recently failed to win full approval from the Nuclear Installations Inspectorate.

It has been ordered to repeat a nuclear emergency exercise.

Shore missiles

Critics - including nuclear safety expert John Large - remain unconvinced by the assurances.

At one stage, it was proposed that Polaris missiles should be stored at the Plymouth base.

Devonport now refits nuclear submarines

A document from 1963 said: "Since Plymouth is to be the operating base for Polaris submarines - Plymouth should be the location for the shore storage of Polaris missiles and their maintenance."

Malcolm Chalmers, of the International Institute of Strategic Studies, says the Admiralty backed away from basing Polaris in the South West because of serious safety fears.

The Polaris missile system was a potent deterrent in the Cold War of the late 60s - and the subject of mass protests.

The nuclear warheads had the ability to obliterate up to 16 cities.

Police operation

Devonport has the largest military dockyard in Europe, covering 650 acres on the River Tamar.

The declassified documents are featured in the BBC South West television programme, Close Up, on Thursday.

Meanwhile police are mounting a major security operation for the arrival this weekend of HMS Vanguard, the first Trident submarine scheduled for a refit at Devonport.

More than 200 officers will be on duty, with many watching the shore to prevent protesters taking to boats to reach the submarine.

The work may be delayed because the government still has to give final approval for an increase in the amount of radioactive Tritium released from the dockyard, though the Environment Agency has not objected.