Rupert Cornwell: As presidential mishaps go, this one takes 'the biscuit'

It has been dubbed "most dangerous handbag in the world" (and not because it weighs in at 45lb). More commonly though – and testament to the pervasiveness of sporting metaphors in American life – it is known simply as "the football". It is the briefcase containing the Pentagon's plans to launch a nuclear attack, and it is supposed always to be with a President when he leaves the White House.

The practice started under Dwight Eisenhower in the 1950s, as the Cold War intensified. And although the Soviet Union no longer exists, "the football", traditionally carried by the White House military aide, has an undiminished mystique. It remains the ultimate symbol of the might of the world's lone remaining superpower, and of its leader's ability to unleash Armageddon.

According to reliable reports, the briefcase contains a "Black Book" setting out the retaliatory options, along with two files. One lists the sites of ready-to-fire missiles, while the other sets out emergency broadcast procedures. It also has an antenna, suggesting there is also electronic equipment inside.

But the most important item of all – and the one that Bill Clinton is said to have lost for months – is "the biscuit", the small card with the top secret codes that authenticate any order for a nuclear strike as coming from the President himself.

The "football" is not the exclusive preserve of the US. Presumably there is a comparable mechanism for a British Prime Minister and a French President to launch their respective country's deterrent, even when they are away from Downing Street or the Élysée Palace.

When he became the first Soviet leader to travel extensively abroad, Mikhail Gorbachev was never far from an uniformed aide carrying a similar briefcase assumed to serve a similar purpose. Indeed, its current exact whereabouts might reveal the ultimate seat of power in today's Russia. Does President Dmitry Medvedev control the Kremlin's nuclear football – or is it Prime Minister Vladimir Putin?