Home Office officials secretly considered plans to provide homes with chemical weapons shelters amid fears of an attack by the Soviet Union — but the scheme quickly ran into difficulties.

Files released by the National Archives show that the plan floundered after experts pointed out that people would have to remain in the sealed shelters for up to 10 hours in the aftermath of a chemical attack — while shelters only had enough air for two to three hours.

It was suggested that the air supply could be extended through the use of fans and filters — but again there was a difficulty.

“It was immediately realised that finding room for them might be a problem,” the minutes from April 1985 noted.