The British government declined on Tuesday to say who had responsibility for the United Kingdom’s nuclear codes while Prime Minister Boris Johnson is treated in intensive care for Covid-19 complications.

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.

Johnson’s personal battle with the virus has shaken the British government just as the United Kingdom enters what scientists say is likely to be one of the most deadly weeks of the pandemic, which has killed 5,373 people in Britain and 70,000 worldwide.

“He’s not on a ventilator,” Gove told LBC radio on Tuesday. “The prime minister has received some oxygen support and he is kept under, of course, close supervision.”

“The prime minister is in intensive care, being looked after by his medical team, receiving the very, very best care from the team at St Thomas’,” Gove said.