The prime minister’s doctor feared that he would not see out the weekend. In Downing Street, the principal private secretary agreed that his boss was probably nearing the end – at least politically, and confided to the paymaster-general that “his articulation and his movements are seriously affected and unless – as is just possible – there is a miraculous recovery in the next forty-eight hours … his office will have to be abandoned.”

“As is just possible … a miraculous recovery,” were the vital qualifiers. Jock Colville knew that however implausible for lesser mortals, extraordinary efforts of willpower were still what set Winston Churchill apart, even although the prime minister was 79 years old at the time.  What comfort may the hero of Boris Johnson’s 2014 book, The Churchill Factor, give his stricken biographer now? And what lessons are there for keeping the machinery of government functioning without its central piston?

In the midst of his second term as prime minister, Winston Churchill suffered a stroke that would have forced any normal leader to quit. It was the most severe of a series of life-threatening illnesses that he had fought off in the preceding ten years – including a heart attack or strain to his chest that felled him at the White House in December 1942, three bouts of pneumonia in 1943 and 1944, and two milder strokes he suffered in August 1949 and February 1952.

But it was the stroke in June 1953 that hit him hardest. It struck suddenly whilst he was hosting a Downing Street dinner for Alcide De Gasperi, the Italian prime minister. One moment Churchill was in full flow, charming his guest by recounting what wonderful things Roman civilisation had brought the Britons, the next minute he was immobilised in his chair. Spotting what had happened, his son-in-law, Christopher Soames, managed to manoeuvre him out and up to bed without the departing guests noticing.

The following day Churchill’s doctor, Lord Moran, diagnosed a stroke and told him to stay in bed. Instead, he chaired a two-hour meeting of the cabinet (as you do when you’re in your eightieth year and been told to rest). Colleagues noticed he was unusually keen to let others do the talking, but otherwise they spotted nothing alarming. However, the next day his condition deteriorated. He was paralysed down his left side. His inner circle began to plan for the worst.

That planning included a comprehensive cover-up. Luckily for Churchill, Parliament was nearing its summer recess so he would soon not be missed in the Palace of Westminster. Able to postpone a summit in Bermuda, there was no pressing crisis he had to be seen to address at home. The major newspaper proprietors were squared with the official line that he was resting after the exertions of the Queen’s coronation earlier that month, and dutifully ensured their publications did not probe further.

In Whitehall, only an inner circle knew about his true state. With unfortunate timing, his natural successor, the Foreign Secretary, Anthony Eden, was also out of action with a gall-bladder operation in the United States. Whilst Churchill recuperated out of view at Chartwell, his Kent country house, the cabinet was chaired by the chancellor of the exchequer, Rab Butler, who fobbed his colleagues off with the explanation that Churchill had felt some strain so was resting for a period, but still seeing important official papers. He would soon be back, no cause for concern.

These are just some of the ways in which Churchill’s stroke – which kept him out of action for a month – was managed in a totally different political climate. In contrast, Boris Johnson has been struck down during his country’s greatest peacetime crisis since the last pandemic, 102 years ago, and with 24 hour rolling news desperate for updates on his condition.

Yet, for all these differences, Churchill’s 1953 stroke remains the obvious historical reference point, if only because there are so few alternative comparisons upon which to draw. Other prime ministers who took ill whilst in office, like Eden and Macmillan, resigned in consequence. If spared, Boris, like Winston, will be back.

In probing exactly how much authority Dominic Raab can assert in Johnson’s absence, it is clear that the 1953 experience offers no workable precedent. Back then, those souls of discretion, the Queen and her private secretary, were informed, but the only members of the government who were let in on the secret were the foreign secretary, the chancellor of the exchequer, the lord president of the council (who also assumed the absent Eden’s duties as foreign secretary), the paymaster-general, the cabinet secretary and the chief whip.

the 1953 experience offers no workable precedent

All got on with their jobs, but none of them assumed ultimate executive authority. There was no “acting prime minister.” The acting was being done by the actual prime minister, who was pretending to be still on top of all the necessary paperwork from his country house.

In reality, the paperwork was being done by the 33-year-old Conservative MP for Bedford, Christopher Soames, who had no authority to be handling such sensitive documents but enjoyed his father-in-law’s confidence, alongside Churchill’s private secretary and the cabinet secretary.

This arrangement has been summarised by the historian, Andrew Roberts, in his peerless biography of Churchill, as an “unconstitutional state of affairs, in which the prime minister’s son-in-law and an unelected private secretary (Jock Colville) held effective executive power in Britain via the equally unelected cabinet secretary.”

They did not abuse that power and by late July Churchill had once again overcome frailty and was able to resume from where he left off. He continued as prime minister until April 1955.

an acting prime minister is not the same as a deputy prime minister

This time the cabinet secretary, Sir Mark Sedwill, will continue to be a conduit for authority – but cannot be that authority itself. Another vital civil servant keeping Downing Street functioning is Martin Reynolds, the prime minister’s principal private secretary. Having previously served Johnson during his tenure as foreign secretary, Reynolds was fleetingly British ambassador in Libya. Such is the current predicament that he could be forgiven for thinking nostalgically of those months in Tripoli.

Unlike in 1953 this hidden wiring does not stretch to imitating prime ministerial authority. Instead, we have what is effectively a new and very public role – that of “designated survivor” which is, in effect, acting prime minister. This is not the same as deputy prime minister, of which there have been several in the past. Even when PMs have been on holiday or at briefly indisposed, deputy prime ministers did not take life and death decisions without their superior’s knowledge and agreement.

Yet, if Boris Johnson is unable to be actively involved for some time, then this is the heavy responsibility that ultimately falls upon his designated survivor, the foreign secretary and first secretary of state, Dominic Raab. Whether Raab is being entrusted with wider executive authority beyond handling the coronavirus crisis, including deciding matters of national security and the ability to hire and fire, is yet to be determined. Officially it seems he does not. But in practice he might – so long as he enjoyed the cabinet’s full confidence (and consequently that of the Queen) in doing so.

As well as praying for the prime minister’s recovery, Raab must also be dearly hoping that when grave and serious decisions need to be taken, he can count on the unanimous support of his cabinet colleagues. He has an unenviable task ahead and no map to follow.