In the days and weeks that ­followed my bout of Covid there was quite a lot of indignant ­internet chatter about the exact severity of my illness. Some said that I was shamming; others that I was indeed ill but that I never needed to go into hospital, let alone occupy an intensive care bed.All I can say is that I felt truly lousy: the scratchy, breathless exhaustion that is ­familiar to Covid sufferers. I also know that at one stage my oxygen levels dropped to 72 per cent, and that below 70 per cent some nasty things start happening to your body.That night in April 2020, the doctors and nurses of St Thomas’ Hospital were preparing, if necessary, to intubate me – spike a hole in my trachea and stuff a tube down my ­windpipe to force-feed oxygen into my lungs.They mentioned the possibility, as they ­prepared to wheel me downstairs.Is that necessary? I said. March 27, 2020: Boris announcing he has tested positive for Covid April 2: He claps for carers after refusing to go to hospital April 3: ‘Slight hitch, folks. I’m not recovering’Oh yes, they said, and made it sound like a routine procedure. What they didn’t explain is that, at that stage in the ­pandemic, patients who were intubated had about a 50 per cent chance of survival. Then I was being wheeled on a gurney into ICU – the intensive care unit.Just ten days earlier I had been in Downing Street with ­colleagues, watching apprehensively as the daily death toll from Covid went on up. At the beginning of March it had been in single figures; now it was well over 200.After one meeting, Chris Whitty, the Government’s chief medical officer, took me aside. He had noticed I was coughing and ­spluttering and red in the face. He suggested I test for the virus. ‘Are you sure?’ I said, knowing that tests were hard to come by. I didn’t want one wasted on me when it could be used for an elderly or vulnerable person. ‘Completely,’ he said.Later that afternoon I went into the Cabinet Room where a doctor in a kind of nuclear waste hazmat suit stuck a probe down my throat. I tested positive.Oh well, I thought. It was a ­nuisance. It might slow me up. But, as I kept telling everyone in those early days of the pandemic, it was generally a mild disease.On the other hand, I also ­remembered my Athenian history. ‘Pericles died of the plague,’ I had earlier reminded my colleague Michael Gove, and his spectacles seemed to glitter at the thought, like the penguin in Wallace & Gromit. As soon as I was diagnosed on March 27, I had gone into self-­isolation in the No 11 flat.Carrie had sequestered herself away from me – since she had not yet tested positive – in the No 10 flat, which still awaited the new Chancellor, Rishi Sunak, and his family, and where camp beds had been laid out in rows in the ­expectation (correct) that people in the building would soon be working round the clock.I had carried on doing my job as best as I could. I had no choice. The country was facing the worst pandemic for 100 years. There was no way I could stop.I began by issuing what I hoped was a fairly jaunty video bulletin. Since no one could stand near me, I made it myself, talking into my phone.Hi folks, I said, I just wanted to let everyone know that – like so many others – I had tested ­positive for Covid and, like so many others, I was now working from home; but be in no doubt, I said, that I was continuing to lead the national effort against the ­disease – and that I was deeply grateful to everyone for what they were doing.Together, I said, in the resolute tones of my recent press ­conferences, we would beat it.I looked bullish, rubicund, as though flushed from a good lunch. Perhaps I sounded a little short of breath, but only if you were ­listening for it.Over the days that followed, as I waited for the disease to go away, I sat hunched over my laptop in my office – obsessively watching the data and trying to direct the UK response.The next day the number of deaths was up again – to a horrifying 463. It was still doubling. When would our measures start to make a difference? When would the curve turn? Deep in my lungs, an allegorical struggle was taking place. Malign little creatures were wreaking havoc in the lining of my airways. Horrible purple or green spheres… they were burying themselves in the soft tissue  The news was getting to me – lowering my spirits, and perhaps lowering my resistance. Perhaps, I wondered blackly, it was some kind of cosmic judgment on me, on my whole worldview – founded as it was on a boosterish faith that our country could get through anything.By Wednesday, April 1, the daily death toll had soared again, to 826, and when I went outside to clap for the NHS and social care workers, everyone looking after the sick, it was noted that I looked pretty groggy.Next day Nick Price the doctor came round to see us both – me because I felt so grim, and Carrie because she was pregnant. He took one look at me and said that I should really get into hospital,as a precaution.No, no, I said. I knew exactly what pressure the hospitals were under. It was ridiculous. I was sure I was on the mend. Boris, with terrier Dilyn, recuperating at Chequers in 2020 after being discharged from hospital He shares a joke with nurses Luis and Jenny, who cared for him in hospital, in July 2020 A cyclist with a poignant message as she makes her way through Westminster in April 2020By the following day – Friday the 3rd – I should have been recovering, according to the usual ­pattern of the disease. I still had a ­temperature. So I composed another breezy video message. Slight hitch, folks, I said: I have still got Covid – but rest assured that the fight goes on.This time I was tie-less, had a face the colour of mayonnaise and was slouching in an armchair. The overall effect was a bit like that character by Paul ­Whitehouse – Rowley Birkin QC – who always concludes his incomprehensible clubland monologues with the payoff line, ‘I was vey, vey drunk’; except in this case I wasn’t drunk. I remembered my Athenian history. ‘Pericles died of the plague,’ I had earlier reminded my colleague Michael Gove, and his spectacles seemed to glitter at the thought, like the Penguin in Wallace & Gromit  By that weekend I was finding it exhausting even to walk. I couldn’t read. I could hardly think. Music grated. All I wanted was for another hour to go by so that I could officially have another couple of paracetamols and that the throbbing in the skull would at least temporarily abate.After a while, Carrie came back in with the painkillers, and though I felt pathetically grateful, I also felt it was ridiculous. I should be caring for her, not the other way round. Not only did she also have Covid, but she was more than eight months pregnant with our first child.Ooof, I said, and tried to take a long breath through the nose. No worst, there is none, said Gerard Manley Hopkins, but then he hadn’t been banjaxed * by Covid while trying to steer a G7 country through a pandemic.That was the trouble – that was why I think I felt so rotten. It wasn’t just the physical distress; it was the guilt, the political embarrassment of it all.I needed to bee-oing-oing back on to my feet like an India rubber ball. I needed to be out there, leading the country from the front, sorting the PPE, fixing the care homes, driving the quest for a cure. By Sunday, April 5, there were more than 1,000 daily ­fatalities across the country. I was still flat out, floating in and out of consciousness, waiting for my fix of paracetamol, when Carrie came in like a ministering angel.’Come on,’ she said. ‘You need to get something to eat.’I said that the kitchen really felt a long way away. So she brought up some apple and cheese. I looked at that cheese with such complete apathy that I knew – after a lifetime as a functioning cheese-oholic – that something was definitely awry.Carrie rang Dr Price and explained things, and then passed the phone to me. He wanted me to come in right away, to St Thomas’ Hospital. No, no, I said. There would surely be people who were far worse off than me – ­people who really needed the bed.He wasn’t having it. You have got to come in, he said. You have now spent too long getting worse, and it has got to the stage where it could go either way.There are people who recover from your position, he said, but then there are also plenty who get suddenly and markedly worse. We need to get you into hospital, because we need to be able to get you oxygen if you need it.Shortly thereafter, Carrie and I were staggering out of the back entrance to No 10, trying to look inconspicuous. We got into a big blacked-out people-carrier, and within a few minutes we had crossed the river and were being wheeled – the doctors insisted on wheelchairs – into the ­bowels of St Thomas’.As soon as I was upstairs and had an oxygen mask on, I started to feel better, though I was still worried about Carrie. At that stage we had no idea whether Covid could be harmful for an unborn child. But the doctors were confident. Her symptoms were much milder, and after a while she went back to No 10.With the oximeter on my finger, we could see that my oxygen levels started slowly to creep up again, and I began to feel sleepy. Before I folded, there was one thing I had to do.I rang Dominic Raab. ‘First Secretary of State,’ I said.’PM,’ he said.’You know I said that you might have to deputise for me,’ I said.’Yes, PM.”Well, that moment has come.”No problem, PM,’ he said. ‘Get well soon.’He didn’t sound remotely rattled – in fact, he went on to do an ­outstanding job.The following morning, having been pumped with a lot of oxygen, I felt ­possibly slightly improved – and more guilty than ever about occupying NHS bed space.I didn’t want to stay there a second longer than I had to, but by the afternoon I seemed to be back to where I was. The oxygen levels kept sinking, and by the early evening I was conscious of a group of gowned and masked doctors, clustered around the doorway. On the whole, they said, they thought that I had better get down into intensive care.The atmosphere in the ­ICU was eerie, the light dim and ­yellow-greenish. As I was pushed to my section at the end of the ward, I glimpsed my fellow sufferers. Some had already been ­intubated and the place was very quiet apart from the wheezing and beeping of the machines.It was like one of those sci-fi movies where a complement of passengers is being transported cryogenically through space.There were about a dozen of us, and we all seemed to be middle-aged men. Some were black, some were Asian, and all, like me, were at least a touch overweight.Then I was being manoeuvred off the gurney and on to the ICU bed – and I met the two nurses whose job it was, that night, to get enough oxygen into my lungs: Jenny from New Zealand and Luis from Portugal.They were both masked up, and it was hard to see their expressions, but they sounded a bit nervous. Which wasn’t surprising. Whatever your politics, no one wants to be the nurse in charge when your prime minister’s vital signs monitor starts emitting that monotonous flatlining beeeeep.Luis fiddled around with the ­oximeter, to check that the levels really were as low as they seemed. Then he instructed me exactly how to lie – slightly over to one side – and propped some cushions beneath me to get it right.I concentrated very hard on breathing.By now, Carrie had alerted my family that I was in the ICU. She was explaining things to my kids, and then I talked to them, too, and to Marina, my ex-wife. Lara, my eldest daughter, resourcefully located some Tintin books to entertain me, but after a while even Tintin was too much.I started to doze, but didn’t want to sleep – partly in case I never woke up, or in case they decided to perform some stealthy tracheotomy without letting me know. So Jenny the nurse handed me an iPad full of films, and I watched a pretty gut-wrenching revenge movie called The ­Revenant, in which Leonardo DiCaprio is a fur-trapper in ­Canada who gets badly mauled by a bear and survives.As the night went on, deep in my lungs, an allegorical struggle was taking place. Malign little ­creatures were wreaking havoc in the lining of my airways. I could visualise them: horrible purple or green spheres, with inverted bog-brushes of protein stuck all over them. They were burying themselves in the soft tissue, using my cells to reproduce. But that night the bear wasn’t Covid. The bear was me. My body, as it was later explained to me, had never encountered Covid before, and my immune ­system was so appalled by this alien life form that it went into a frenzy – a ‘cytokine storm’, in which the immune system fires ack-ack indiscriminately at friend or foe alike and the body is under attack from itself.It was a rough night, but by daybreak it felt as if the storm had broken. Luis and Jenny had been at it more or less ­constantly – ­shifting me by a couple of inches, checking the ­oximeter, tilting me so that the oxygen could get where it needed. Now my ­numbers were better – not exactly Olympic, but better. I was amazed by how weak I was, physically wrecked, as though I had been in a car crash. I could hardly move, and the doctors were insistent I should stay another couple of days in ICU.From my bed I looked out of the window on to a building site. Part of this great and ancient hospital was being rebuilt – a ­project I’d had a hand in when I was mayor of  London. I stared down at this hole in the ground and reflected how I had come within an ace of having a hole dug for me. Why had I got so damn ill? The way particular people can be badly affected by a new virus is partly genetics. But it didn’t help much that, like so many of us Brits, I was fat.I had also been exposed – I ­suspect – to a very large viral load: that is to say, I had been in many meetings with people who may have had Covid, but who did not necessarily have symptoms.I was also exhausted, emotionally shattered by watching the ­disease roll in, wave after wave, and knowing that there was ­relatively little I could do.I didn’t realise it, as I languished, but my fate was being watched with fascination around the world. Donald Trump dispatched ­representatives of the US pharmaceutical industry, to revive me with drugs not licensed or approved in the UK.Congregations were apparently praying for my good health, and it may sound weird, but I am truly grateful for all such intercessions. I expect that some people were of course praying that one way or another the disease would mean the end of me, at least politically.One thing is for certain: at the moment it was announced I was going into ICU, when there was therefore believed to be a genuine chance that I was about to die, my popularity figures were higher than any PM in history.I left hospital on Easter ­Monday and drove to Chequers with Carrie – BBC helicopter overhead – for a two-week convalescence.Here I sat for much of the first few days, slumped in a chintzy armchair in front of a fire, going through my red box or asleep.On Thursday evenings, as a goodly chunk of the population were by now standing outside their homes, clapping and ­banging saucepans in honour of those working in healthcare. ­Carrie and I turned out too, on the steps of Chequers.I clapped with deep emotion because my lungs were telling me that I had been through something really pretty nasty, and that if it hadn’t been for Jenny and Luis, fiddling with those oxygen tubes all night with all their skill and experience, I think I might have carked it **.On the day I was released, the virus had killed 737, and the daily toll was still rising. We were going to hit 10,000 fatalities and the gradient of the curve seemed steeper than that of France or Spain or Italy.The frustration was appalling. I longed to be able to get back to my desk, to steer things – but my body had other ideas.On about the second or third day, I had tried to have a swim in the Chequers pool (donated by a former US ambassador, after President Richard Nixon paid a visit to Edward Heath and was horrified to discover that the British prime minister was expected to survive without one).Margaret Thatcher had been so hostile to this luxury that she turned the heating off, but when I was there the water was ­generally pretty warm. Now, it felt freezing. I am a strong swimmer, but I could barely manage a length, and had to haul myself out at the side. I lay there ­gasping like a grampus ***.It was an effort to get up the stairs, and climbing the hill was impossible. So I walked along the flat ground, with Dilyn pulling like a husky, until I noticed to my horror that even Dilyn seemed suddenly to have succumbed. After a few hundred yards he would lie there all floppy, tongue lolling. I have never seen anything like it before or since, and scientist Patrick ­Vallance later told me his dog had been the same. It felt like a medieval chronicle of a pestilence so bad that even the dogs were struck down.This virus was new, and deadly, and we did not know which way the pandemic would turn.British scientists were the first to come up with a genuinely ­useful treatment for the disease, by showing that the steroid ­dexamethasone could stop the nasty immune reaction – the cytokine storm.It came too late for me, but it was a chink of light, a hint that one day the cavalry would appear tootling over the hill, and medicine would come once again to the rescue of the human race.But when?DICTIONARY CORNER* Banjaxed – broken, ruined, shattered (Irish/English slang)** Carked it – died (Australian slang)*** Grampus – a type of dolphin Obama’s Brexit put-up job In the lead-up to the referendum, David Cameron invoked the aid of Barack Obama, who flew in on Air Force One like a kind of deus ex machina * and obligingly poured scorn on the idea – dear to many ­Brexit-backing hearts – that we might get a post-Brexit free-trade deal with the US.Britain would be ‘at the back of the queue’, said Obama, his choice of words (‘queue’ being British English for what ­Americans call the ‘line’) revealing that he had been fed the script by No 10.DICTIONARY CORNER * Deus ex machina (Latin: god from the machine): an unexpected power or event saving a seemingly hopeless situation.