IN A ritual out of sight of the cameras on Inauguration Day in January, America’s “nuclear briefcase” will change hands and President Donald Trump will receive a card, sometimes known as the “biscuit”. The card, which identifies him as commander-in-chief, has on it the nuclear codes that are used to authenticate an order to launch a nuclear attack. At that point, should he wish, Mr Trump can launch any or all of America’s 2,000 strategic nuclear missiles.

There are no constitutional restraints on his power to do so. Even if all his advisers have counselled against it, as long it is clearly the president giving the command, the order must be carried out. There are no checks and balances in the system. Moreover, once the order is given there is likely to be only a matter of minutes in which it could be rescinded. Once the missiles are flying, they cannot be called back or disarmed. Mr Trump, from what he has said, does not take this responsibility lightly. Indeed, he has often stated that he believes nuclear weapons to represent the greatest threat to humanity and that he will not be trigger-happy, “like some people might think”. But in common with his predecessors, he does not rule out their use.

With little more than ten minutes to take a decision that could kill hundreds of millions of people, even the calmest individual would be under intolerable stress if informed that America was under imminent attack. It is not Mr Trump’s fault that the system, in which the vulnerable land-based missile force is kept on hair-trigger alert, is widely held to be inherently dangerous. Yet no former president, including Barack Obama, has done anything to change it.

Of greater concern would be how Mr Trump might behave in an escalating confrontation if Russia were to rattle its nuclear sabre even more loudly. It is possible that his apparent desire to be buddies with Vladimir Putin might help defuse a dangerous situation. He is, however, notoriously thin-skinned and unable to stop himself responding to any perceived slight with vicious (verbal) attacks of his own. He also revels in braggadocio and is known to be reluctant to take advice. Marco Rubio, a rival for the Republican nomination, questioned whether he had the temperament to be put in charge of the nuclear codes. So did Hillary Clinton. They were right to do so. But it is now Mr Trump, not them, who takes the biscuit.