When asked by the BBC if Foreign Secretary Dominic Raab had been handed the nuclear codes while Johnson receives treatment, Cabinet Office Minister Michael Gove said: “There are well-developed protocols which are in place.”

“I just really cannot talk about national security issues,” Gove said.

The United Kingdom is one of the world’s five official nuclear-weapon states and has four nuclear submarines armed with Trident II D5 ballistic missiles loaded with nuclear warheads.

The United Kingdom has a stockpile of about 215 nuclear warheads, though about 120 are operationally available.

Only the British prime minister can authorise a nuclear strike. Such an order would be transmitted to one of Britain’s nuclear submarines with a special set of codes.