Prince Philip believed the Cold War nuclear arms race was “ridiculous” and supported disarmament, it has been reported.

Previously unpublished letters have emerged in which the Duke of Edinburgh said he was “in favour of multilateral disarmament”.

The Times reported that, writing to Labour peer Lord Brockway in February 1981, the Duke said he believed “it was possible that there had not been another major war in the last 30 years because world leaders realised what a horror they would unleash”.

Lord Brockway had sent him a copy of a speech by the Duke’s uncle, Earl Mountbatten, in which the elder statesman had told a Stockholm audience: “As a military man who has given half a century of active service, I say in all sincerity that the nuclear arms race has no military purpose.

“Wars cannot be fought with nuclear weapons. Their existence only adds to our perils.”

Philip’s reply to Lord Brockway stated he agreed with “everything” Mountbatten had said. He denied reports that in an address of his own he had said he believed a “successful defensive nuclear war” was possible, The Times reported.

Earlier this year the Duke stepped down from his ceremonial role as Captain General of the Royal Marines after more than 60 years, handing it to Prince Harry.