Bill Clinton was an American president of charisma and vision. But he did not always have the patience for the peskier details of his job – like never, ever forgetting to have those nuclear launch codes in his top pocket, or at least somewhere on his person.

According to a former top military official at the time, Mr Clinton managed to mislay not for hours, but for months, the special plastic card with the codes that in military and White House parlance is called "the biscuit". Without it, the president is theoretically unable to order a nuclear launch.

The extraordinary revelation comes towards the end of a new memoir from General Hugh Shelton, who served under President Clinton as the Chairman of the Joint Chiefs of Staff, called "Without Hesitation: The Odyssey of An American Warrior".

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General Shelton, who spoke about the book on ABC News yesterday, wrote: "At one point during the Clinton administration the codes were actually missing for months. That's a big deal – a gargantuan deal."

Scholars of Clinton's time in the White House will not be entirely surprised by this news. No one could rival him for detailed knowledge of policy, but time-keeping, the ability to stick to a schedule and other more mundane functions were not Clinton's speciality.

Retired Air Force Lieutenant Colonel Robert Patterson, a well- known critic of the former president, told a strikingly similar tale of absent-mindedness in his own book about his years of service. Patterson, who at times carried the launch briefcase, known as "the football", for the president, claimed that the day after the story about Mr Clinton and his liaison with former intern Monica Lewinsky first broke, he asked him for "the biscuit" only to discover that the Commander-in-Chief couldn't find it.

"He thought he just placed them upstairs," Patterson wrote. "We called upstairs, we started a search around the White House for the codes, and he finally confessed that he in fact misplaced them. He couldn't recall when he had last seen them."

It may be that Mr Clinton was so confident that the threat of nuclear warfare was over that he felt the biscuit-carrying tradition was superfluous. Alternatively, the lapse – if the claims in the memoirs are true – might be considered as evidence as carelessness verging on dereliction of duty.

The secrecy that necessarily accompanies the arrangements for a nuclear launch has created a degree of mythology about American presidents and "the football". Most of the mechanics of ordering a launch in retaliation for an attack against the United States, have become public over the years.

Wherever the president travels, a military aide stays close with "the football", a black briefcase, which appears to have an antenna protruding from it. The case contains a booklet setting out the options for nuclear retaliation and has the communication capacity to connect him with the Pentagon and Central Command.

Crucial to the system, however, is "the biscuit". On it are printed a series of codes that the president must read out prior to ordering a launch. Only when commanders hear these codes will they know for certain that it is the president talking. Thus, an almost comic scene springs to mind had Mr Clinton ever found himself in the middle of a nuclear strike crisis. As the warheads of an enemy nation sped around the globe towards an American metropolis, the president would be fumbling through his pockets like a passenger at airport security.

Still, he may not be the only Democrat former commander-in-chief with biscuit crumbs, if not egg, on his face. There have long been tales around the White House – never confirmed though – that the President Jimmy Carter once sent a suit to the dry cleaners with the card and the secret codes inside.