By William James and Alistair Smout

LONDON (Reuters) – British Prime Minister Boris Johnson was stable in intensive care on Tuesday after receiving oxygen support to help him battle COVID-19, while his foreign minister led the government’s response to the outbreak.

The upheaval of Johnson’s personal battle with the virus has shaken the government just as the United Kingdom, now in its third week of virtual lockdown, enters what scientists say will be the most deadly phase of the pandemic which has already killed 5,373 people in the country.

A general view of police officers outside the St Thomas’ Hospital after British Prime Minister Boris Johnson was moved to intensive care while his coronavirus (COVID-19) symptoms worsened and has asked Secretary of State for Foreign affairs Dominic Raab to deputise, London, Britain, April 7, 2020. REUTERS/Henry Nicholls

Johnson, 55, was admitted to St Thomas’ Hospital across the River Thames from the House of Commons late on Sunday after suffering persistent coronavirus symptoms, including a high temperature and a cough, for more than 10 days.

But his condition rapidly deteriorated over the next 24 hours, and he was moved on Monday to an intensive care unit, where the most serious cases are treated, in case he needed to be put on a ventilator. He was still conscious, his office said.

“He is receiving standard oxygen treatment and breathing without any other assistance,” Johnson’s spokesman told reporters.

“The prime minister has been stable overnight and remains in good spirits,” the spokesman said. “He has not required mechanical ventilation, or non-invasive respiratory support.”

But the absence of Johnson, the first leader of a major power to be hospitalised after testing positive for the novel coronavirus, has raised questions about who is truly in charge of the world’s fifth largest economy at such a crucial time.

While Britain has no formal succession plan should a prime minister become incapacitated, Johnson asked Foreign Secretary Dominic Raab, 46, to deputise for him “where necessary”, Downing Street said..

Queen Elizabeth wished Johnson a “full and speedy recovery” and sent a message of support to his pregnant fiancée, Carrie Symonds, and his family.

WHO LEADS?

Raab on Tuesday chaired the government’s COVID-19 emergency response meeting, though ministers refused to say who had ultimate control over the United Kingdom’s nuclear weapons – a role held by the prime minister.

“There are well-developed protocols which are in place,” said Gove, who himself went into self-isolation on Tuesday after a family member displayed coronavirus symptoms.

British leaders do not traditionally publicise the results of their medical examinations as some U.S. presidents including Donald Trump have.

Raab, the son of a Czech-born Jewish refugee who fled the Nazis in 1938, takes the helm at a pivotal time. Government scientists see the death toll rising until at least April 12 and Britain must ultimately decide when to lift the lockdown.

Johnson’s move to intensive care added to the sense of upheaval that the coronavirus has wrought after its spread caused global panic, sowed chaos through financial markets and prompted the virtual shutdown of the world economy.

The United Kingdom is in a state of virtual lockdown, a situation due to be reviewed early next week, and some ministers have suggested it might need to be extended because some people were flouting the strict rules.

The pound dipped in Asian trading on news of Johnson’s intensive care treatment but then rallied in London trading. Against the dollar, sterling traded to a high of $1.2349, up 0.9% on the session.

CRITICISM

Even before coronavirus, Johnson had had a tumultuous year.

He won the top job in July 2019, renegotiated a Brexit deal with the European Union, fought a snap election in December which he won resoundingly and then led the United Kingdom out of the European Union on Jan 31 – promising to seal a Brexit trade deal by the end of this year.

The government has said it is not planning to seek an extension to that deadline in light of the epidemic.

Johnson has faced criticism for initially approving a much more modest response to the coronavirus outbreak than other major European leaders, though he then imposed a lockdown as projections showed half a million people could die.

He tested positive for the virus on March 26.

After 10 days of isolation in an apartment at Downing Street, he was admitted to hospital. He was last seen in a video message posted on Twitter on Friday when he looked weary.

James Gill, a doctor and a clinical lecturer at Warwick Medical School, said the news of Johnson’s admission to intensive care was “worrying” but not completely out of line with other people suffering complications.

(Additional reporting by Paul Sandle, Michael Holden, Costas Pitas, Kylie MacLellan, Alistair Smout and Kate Kelland; Writing by Kate Holton, Elizabeth Piper and Guy Faulconbridge; Editing by Angus MacSwan)