Boris Johnson has asked Foreign Secretary Dominic Raab to deputise for him ‘if necessary’ while the Prime Minister is in intensive care.
But the coronavirus crisis has brought the UK’s fuzzy, unwritten constitution into focus - with many people confused about who is actually in charge.
And even with Dominic Raab filling in for the PM in cabinet meetings and other duties, it’s unclear how far his powers reach.
And it’s far from certain who would replace the Prime Minister if he dies suddenly or is incapacitated for a long period.
In the United States, which has a strict written constitution, there are well developed procedures in place for when a President is incapacitated.
There’s a legal line of succession, running from the Vice President, through the Speaker of the House and President pro tempore of the Senate, then right the way through the Cabinet.
Currently, some 13 people would have to die or be incapacitated before Secretary of Housing and Urban Development Ben Carson became President.
In fact, that’s more or less the plot of the TV show Designated Survivor.
But in this country, we have neither a strict, written constitution nor a legal line of succession so everything becomes a little more…murky.
Here’s what we know.
Does Boris Johnson have a deputy?
When he formed his first cabinet, Boris Johnson chose not to have a formal Deputy Prime Minister.
It’s not a requirement, and most PMs don’t. David Cameron had Nick Clegg as his deputy, but that was mostly to keep the coalition government afloat.
Instead, there’s a slightly vague convention that the First Secretary of State deputises for the PM if they can’t do the job.
First Secretary of State isn’t really a job - it’s a title someone has to imply seniority over other Cabinet ministers.
It’s also worth remembering that even though Nick Clegg was Cameron’s Deputy PM - he named former Tory leader William Hague First Secretary of State.
Currently, the title belongs to Foreign Secretary Dominic Raab.
Number 10 said last night that Boris Johnson had asked Mr Raab to deputise for him “if necessary.”
Who takes over if Dominic Raab becomes ill?
This afternoon the Prime Minister's official spokesman said if Mr Raab became incapacitated, then rookie Chancellor Rishi Sunak would take over from him.
The spokesman said: "There is an established order of precedence. The Prime Minister has you know appointed the Foreign Secretary as his First Secretary of State.
"In line with the order of precedence the Chancellor would follow from the Foreign Secretary."
Why isn’t there an official deputy?
Because - technically - the country is run by the Cabinet rather than the PM alone. The Prime Minister is supposed to be ‘first among equals’ in the Cabinet.
Can Dominic Raab reshuffle the cabinet in Boris Johnson’s absence?
Apparently not.
The PM's official spokesman was asked if Mr Raab could do any hiring and firing of ministers in the Prime Minister's absence.
He replied: "The short answer to that is no."
Who’s in charge of the nuclear weapons if the PM is incapacitated?
That’s a very good question.
In theory, Dominic Raab as First Secretary of State could authorise military action - but he would most likely have to obtain the support of senior cabinet ministers to do so.
Boris Johnson's official spokesman said: "In relation to national security matters the First Secretary of State and the Cabinet have the authority and ability to respond in the Prime Minister's absence.
"The UK has robust national security architecture, including the National Security Council (NSC), which is designed to be resilient and able to operate effectively under different circumstances."
"Should any NSC be required the Foreign Secretary would chair it."
He added: "In relation to nationa security decisions are taken by the Cabinet. The Foreign secretary would chair any Cabinet meeting."
There’s also the question of the so-called ‘letters of last resort’ - which the PM writes to give instructions to nuclear commanders in case he’s killed in an attack.
Number 10 say Mr Raab has not been asked to write letters of his own, because "the Prime Minister remains the Prime Minister."
But if Mr Johnson is out of action for a long time - or if he stepped down - someone else may be asked to write letters of their own.
Will Dominic Raab take over Boris Johnson's weekly audience with the Queen?
No.
Number 10 say the Queen and Buckingham Palace have been in constant contact and are getting updates on the PM's condition.
But instead of Mr Raab having a weekly meeting with the monarch, as the PM usually does, senior officials - specifically Cabinet Secretary Mark Sedwill and the Prime Minister's Principal Private Secretary will continue contact with the royal household on his behalf.
What happens if Boris Johnson dies or steps down
In either case, a new Prime Minister would have to be appointed by the Queen.
Usually, the Queen instructs the leader of the largest party to form a government - but that wouldn’t automatically be Dominic Raab.
It would be up to the cabinet to recommend an immediate successor to the Queen.
The Tory rulebook requires the party to hold a leadership election if the PM dies in office.
But there’s no official ‘acting’ or ‘interim’ Prime Minister role. Whoever the Queen approves is full-on Prime Minister. It would be up to them to resign as PM once the leadership election is completed and a new party leader is selected.
Wouldn’t it be better to have a formal, written line of succession?
Some people think so, yes.
Tory MP Peter Bone has been asking for a strict line of succession to be written into law for almost a decade now.
In March he called on the government to back his Bill so it could be in place in case the PM falls ill with coronavirus.
"Nobody seems to be able to tell me what happens if the Prime Minister is incapacitated," Mr Bone told the Mirror.
"Maybe there's a letter somewhere that says who's in charge."
He added: "In a national emergency, you don't want to be scrabbling around worrying about who's in charge.
"And you don't want the Foreign Secretary and the Cabinet Office Minister arguing about who's in charge."
Mr Bone has a private members' bill progressing through the Commons - but it's unlikely to progress without the backing of the government.
