British cabinet papers from 1975 detailing the government's plans in the event of nuclear war are among new documents released by the National Archives. They reveal that government bunkers would be manned by civil servants, emergency legislation would be passed, and hospitals would be emptied.

TV was to close down, and the BBC to begin a wartime service on radio. The prime minister would be taken to his bunker but there were no plans at that time to evacuate civilians.

The information is among a raft of unseen material that has been revealed in government records from 1975, now released to the public at the National Archives in Kew, south-west London.

On the preparations for a nuclear attack historian Peter Hennessy told the BBC's Sanchia Berg the documents were the most secret he had ever seen.

He said: "These were the Crown Jewels of genuine official secrecy...because you didn't want the other side to get your war plans.

"Also the degree of alarm for the civilian population, in relatively tranquil times, that a leakage of this would have produced would have been extraordinary."