Defence chiefs warned seven years before the Falklands War that the islands would be almost impossible to defend in the event of an Argentine invasion, according to official papers made public.

Files released to the National Archives in Kew, west London, under the 30-year rule show that in 1975 Defence Secretary Roy Mason urged Prime Minister Harold Wilson to seek a "political solution" to the long-running dispute over the islands.

A Ministry of Defence briefing note from February 1975 warned that the problems of providing a force sufficient to defend the islands in the face of an invasion were "formidable".