There are growing fears in Whitehall that the UK could face a national emergency in which Boris Johnson’s caretaker government has to take key decisions.
The current British Prime Minister remains in charge of government, potentially facing crucial judgments, while the Conservative Party chooses a new leader.
That process may last until September, leaving three months in which Britain could face a national or international emergency that requires a rapid government response.
There is a Whitehall manual giving some guidelines for a caretaker government, although a substantial amount relies on convention and the British “good chap” constitutional model of “doing the right thing”.
Sir David Normington, the former civil service Home Office chief, said there would be issues over urgent decisions, particularly now that Mr Johnson has lost his authority.
“We are in slightly uncharted waters because there are no rules about a transition like this as there are only conventions,” he said.
A caretaker prime minister “should not be taking major decisions about future policy”, he told the BBC, but that could prove problematic given the war in Ukraine and a looming economic crisis.
“It's called a caretaker government, but in a national emergency it has to act and that's why you have to have a prime minister in office and you have to have a Cabinet reacting to the situation,” he said.
“There would be a rallying round and agreement about what action should be taken, but it is very difficult with a prime minister who is a caretaker and has lost authority.”
The government will push ahead with trying to force through deportations of asylum seekers to Rwanda, No 10 Downing Street said.
"This is a pre-agreed government policy," the prime minister's official spokesman said. "Convention doesn't prevent or preclude government from seeking to fulfil that policy and that would include defending cases in court as required."
It is possible flights taking asylum seekers to Rwanda could depart before a judicial review, the spokesman said.
On Friday, there were a number of additions to the new Cabinet, including Peter Bone who becomes the deputy leader of the Commons, while Andrew Griffith was appointed parliamentary under-secretary of state at the Department for International Trade.
There are two checks on Mr Johnson’s power, but both rely on convention rather than rule of law.
The Cabinet will act as a restraint on any rash actions, and with the recent appointment of respected figures such as Sir Robert Buckland and Greg Hands this may provide some comfort.
Another similar new appointee, the former Middle East minister James Cleverly, who is now Education Secretary, said that Mr Johnson had given assurances to his hastily assembled new Cabinet on Thursday that he would do nothing untoward.
“The prime minister made explicit references to Cabinet that we are not going to do anything that would tie the hands of our successors,” Mr Cleverly said. “We are not going to do anything that would be novel or a big change from the current set direction of travel.”
The Cabinet secretary Simon Case may also check any rash or untoward actions. However, given his current record in Downing Street, which included overseeing the illegal lockdown parties in which he was pictured with Mr Johnson, his authority has been undermined. Sir David described Mr Case's experience of working alongside the prime minister as akin to “being a bystander at a car crash”.
A comparison can be drawn between when an incumbent US president is defeated in elections held in early November, only to remain in the White House making decisions for the best part of another three months.
There were fears that Donald Trump would behave erratically after he was voted out in 2020, and that prediction was fulfilled with the storming of the US Capitol on January 6.
Those fears may well impel the 1922 Committee, which sets Conservative Party rules, to speed up the leadership contest so that it is completed rapidly, with a new prime minister and Cabinet in post before the end of the summer.
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