For 16 hours from the 27 to 28 October 1961, US and Soviet tanks faced each other in divided Berlin and the two superpowers came closer to kicking off a third world war than in any other cold-war confrontation, bar the Cuban missile crisis a year later.

In August 1961 Washington and its British and French allies had failed to prevent the Russians building the Berlin Wall. And by October, East German officials had begun to deny US diplomats the unhindered access to East Berlin that was part of the agreement with Moscow on the postwar occupation of Germany.

Then, on 22 October, E Allan Lightner Jr, the senior US diplomat in West Berlin, was stopped by East German border guards on his way to the state opera house in East Berlin. The East Germans demanded to see his passport, which he insisted only Soviet officials had the right to check. Lightner was forced to turn back.

General Clay, the pugnacious American hero of the 1948-49 Berlin Airlift who had been sent by Washington to deal with the Russians after the erection of the Berlin Wall, ordered that the next American diplomat entering East Berlin was to be escorted by armed US army military police in jeeps. The manoeuvre succeeded, but the East Germans continued to attempt to assert their claim to control western allied officials entering East Berlin.

Never one to suffer defeat easily, Clay ordered American M48 tanks to head for Checkpoint Charlie. There they stood, some 75 metres from the border, noisily racing their engines and sending plumes of black smoke into the night air. Alarmed by the apparent threat, Moscow, with the approval of the Soviet leader, Nikita Khrushchev, sent an equal number of Russian T55 tanks rumbling to face down the Americans. They too ground to a halt some 75 metres from the East/West Berlin border and, as with the US tanks they faced, stayed there for 16 hours.

By now, American officials were deeply alarmed by the potential consequences. General Clay was reminded by Washington that Berlin was not so "vital" an interest to be worth risking a conflict with Moscow. President Kennedy approved the opening of a back channel with the Kremlin in order to defuse what had blown up.

As a result, the Soviets pulled back one of their T55s from the eastern side of the border at Friedrichstrasse and minutes later an American M48 also left the scene. So it went until all the behemoths were withdrawn. General Clay's reputation among West Berliners had risen further but his warrior days were effectively over.

Khrushchev had been equally uninterested in risking a battle over Berlin. In return for Kennedy's assurance that the west had no designs on East Berlin, the Soviet leader tacitly recognised that allied officials and military personnel would have unimpeded access to the East German capital.

From that point on, the western allies freely dispatched diplomats and military personnel to attend the opera and theatre in East Berlin. Soviet diplomats, too, attended functions in West Berlin and sent Volga limousines packed with Soviet military police on patrol to West Berlin. The elaborate routine served to prove that the Four Power status of the city was intact. It was faithfully observed until the Wall fell in November 1989.