Britain came close to war with the Soviet Union in 1968 when it became convinced by intelligence reports that Moscow was about to invade Romania, the Observer reported yesterday.
Quoting previously secret government papers released to the public on Saturday, it said the Labour prime minister, Harold Wilson, had ordered contingency plans to thwart what he feared would be a Soviet push into Romania and possibly Yugoslavia.
The Romanian president, Nicolae Ceausescu, had condemned Moscow's crushing of the Prague Spring reforms when Warsaw Pact forces invaded Czechoslovakia on August 20th, 1968, and, according to the Observer report, Moscow was determined to teach him a lesson.
Minutes from British government meetings in September 1968 quote the defence secretary, Denis Healey, as saying Britain could not stand idly by while President Leonid Brezhnev drove Soviet expansion forward.
The Norwegian daily Aftenposten last week quoted newly-released papers saying Oslo had issued soldiers with live ammunition in June that year when Moscow massed tanks within 30 metres of their Arctic border.
In Britain plans were put in place to send crack troops to Yugoslavia to arm and organise guerrilla resistance if Belgrade came under direct threat.
Tension continued to rise, and by November 19th, 1968, Britain believed an invasion of Romania was imminent after a Dutch intelligence report claimed that 150,000 Soviet, Polish and Hungarian forces planned to move on Bucharest on November 22nd.
The Public Record Office file ends without giving any details about how the tension was defused. But the Observer quoted Wilson's biographer, Ben Pimlott, as saying Moscow's backdown was a defining moment.