Margaret Thatcher's senior aides used pictures of a baby Prince William to divert attention from a major peace march against the deployment of US nuclear missiles in the UK, newly released government files reveal.

Papers released by the National Archives at Kew, west London, show ministers feared the scale of the protests at the Greenham Common airbase in Berkshire could prevent the stationing of the missiles going ahead.

The move to deploy US cruise missiles to Britain and other European countries in 1983 after Russia targeted its SS-20 missiles on the West came at one of the tensest moments of the Cold War.

As a women's peace camp was established at Greenham Common, foreign secretary Francis Pym advised Mrs Thatcher there was a risk the demonstrations could become so widespread that "deployment would actually become difficult or even impossible".

In Number 10 Mrs Thatcher's press secretary Bernard Ingham feared the consequences.

Only "a North Sea blow out, an assassination attempt on the Pope, etc - some awful tragedy" could knock the protest off the news schedules, Mr Ingham fretted, adding hastily: "All tragedies are devoutly not to be wished".

He then came up with the idea of using the visit to Australia of Prince Charles and Princess Diana, with their nine-month-old son William, to try to draw the media attention away from the demonstrators.

"What would take the trick would be press and TV pictures, for TV release on the evening of Good Friday and/or Saturday newspapers of Prince William in Australia."

By the autumn, with the first missiles set to arrive at Greenham Common, Defence Secretary Michael Heseltine informed Mrs Thatcher there would be four infantry battalions on standby in case of any trouble from the demonstrators.

At the same time, he disclosed that RAF personnel would be "covertly" inserted into the base, with a small number of armed personnel "operating very close to the armed US personnel and with the same rules of engagement".