It's February, it's freezing cold, and George Garton is in pre-season training with Sussex, a few weeks after making his England debut in a T20I in Barbados. He has struggled to meet his usual standards in fitness tests after returning to Hove, which he puts down to the fact he was away all winter and hardly had time to train. But he can tell it's more than that.
Every time he tries to push himself, he feels an acute shortness of breath and a level of fatigue unfamiliar for a fit, young athlete - not least a fast bowler who has been clocked at 90mph. His coaches are concerned and say they will try to ease him back into bowling, with the county season still two months away.
Then one morning, he bowls an over in the nets in the marquee on the square, and his body lets him know that it wants him to stop. "I felt really light-headed, and a bit dizzy," Garton says. "And my body just started shaking, quite violently. That was when I was like, 'Oh crap, something's really not right.'"
Three months later he is so exhausted and demoralised after playing a County Championship fixture against Middlesex that he contemplates retirement from professional sport at the age of 25. Garton, a left-arm seamer with a slingshot action, whose six-hitting and ability in the field led Mahela Jayawardene to describe him as "a great package", has fought his battle with Long Covid away from the public eye but he is ready to tell his story.
"The next day a couple of lads felt really rough," Garton says. "Everyone got tested, and three or four people got pinged. As it went on, more and more of us ended up having it. A few of the lads - Woody [Mark Wood], Sam Billings, Daws [Liam Dawson] got stuck at the hotel. Thankfully I managed to get home before I tested positive, but that was pretty bad: I was bed-bound for three or four days."
Garton missed one game in the Hundred last summer with post-viral fatigue, but recovered to play a starring role in Southern Brave's title win, having impressed for Sussex in the T20 Blast. He earned an IPL deal as a replacement player for Royal Challengers Bangalore, played five games in the UAE, then travelled to Australia, where he struggled during a stint with Adelaide Strikers in the BBL.
When in mid-January this year England called him up for their T20I series in Barbados, they asked him and five other squad members to leave the BBL early. In theory, the idea was that they could follow safe-living protocols at home in order to minimise the risk of catching Covid before the series; in practice, Garton contracted the virus for the second time, most likely on the plane home. At the time, the illness did not seem severe.
"I felt okay," he says. "We only had to isolate for six or seven days, so I did that at home and shut myself away. It was kind of like a cold. I went to Barbados, felt absolutely fine, trained, played, came home, went on holiday with my dad for a week and then cracked on with training at Sussex."
After his near-collapse in the pre-season marquee, Garton was told to visit Dr Rachael James, a cardiologist in the local hospital, who administered MRI scans and blood tests to diagnose the problem. "I had an ECG attached to me for 48 hours: all those tests came back pretty much clear. They found a little bit of myocarditis, which is scarring of your heart, but that can happen from any sort of virus; they found that the electrical side of my heart was working fine."
The problem was that his heart rate was alarmingly high. "My resting heart rate is from anywhere from 50-60 [beats per minute] but it was sitting at 75-80. As soon as I did anything - even standing up to go to the kitchen to get a glass of water - it would go to about 100. And it wouldn't come back down after exercise. I'd go to bed six hours after training and it was still about 100.
"The cardiologist said that was probably why I was getting quite tired and quite fatigued: my heart and my body weren't getting any rest. When your body is fighting a virus or whatever, it goes into a kind of survival mode and everything heightens up. She said that my body was kind of still doing that, thinking that it had to fight a virus that actually wasn't there."
Garton took a couple of weeks off to rest. His heart rate started to come back under control as a result. He lined up a comeback game against Middlesex in May, but it quickly became clear he was still in serious trouble.
"I batted for nearly two hours on the first day, from just after tea until the close. I remember I called on some drinks and said, 'Look, I need three cans of Red Bull and some Pro Plus. I need something to keep me awake because I'm really struggling.' I remember getting home and my heart rate was about 100 all the time. I tried to bowl in the game and managed about four-over spells and not very many overs  in the game.
"That was when it got really frustrating from a mental point of view. It's definitely the hardest injury I've ever had: I've torn my side four times, torn my hamstring. I've had my fair share of muscular injuries, but at least for those, there's a time frame and people know about them. There have to be hundreds of thousands of athletes that have torn their hamstring. With Long Covid, no one knew."
Garton gradually became aware from speaking to his cardiologists that young athletes are at a much greater risk of experiencing long-term Covid issues than common perception suggests. "Because we train so hard and everything's kind of functioning as efficiently as it can, there's more to go wrong - that was how they explained it to me."
The Office of National Statistics estimated that two million people - around 3% of the population - were living with Long Covid in the UK in June 2022, with comparatively low vaccination rates among younger age groups meaning that they are over-represented among sufferers.
Garton spent hours speaking to Michael Yardy, Sussex's academy coach, who has a master's degree in psychology and struggled with anxiety and depression during his own career.
"I had to try and understand that it was a real injury. If you've torn your hamstring, you can't run. You physically can't do it. With my cardiac issues, when I woke up in the morning, there was nothing stopped me from doing something apart from feeling tired. I guess there's a little bit of a stigma around that because everyone's tired: nobody ever feels fresh, no one's 100%. Trying to tell coaches and peers that the reason you're not doing things is because you're tired - I felt embarrassed. You almost feel like you're being soft...
"It was a big struggle, at the worst of it. I live two minutes from the ground: I would walk to the ground and have to sit down and rest for half an hour because I was really out of breath. Mundane tasks, like walking up the stairs to my flat or taking the bins out, that was a big struggle. It was pretty tough."
It could not have helped his confidence that the medical fraternity did not quite know how to treat his condition. "The cardiologists themselves owned up and said, 'We don't know what's going on.' I became pretty low. After the Middlesex game, the coach [Ian Salisbury] was saying, 'We can manage you through games', but I just thought, 'I don't want to do that.' If that was all I could do, I just thought, 'I'll retire now because I can't put myself through that pain of not being able to do what I expect myself to do.'
"I genuinely thought that if it didn't get better, that's it, I'm done. I can't play at 70% all the time. As much as everyone at Sussex was helpful and supportive, saying, 'You at 70% is still really good for us,' I just thought 'I can't'. That game, I felt like I'd really damaged our chances of getting a draw or a win. When I was expected to bowl, I was unable. It was the first time I'd had to tell the captain, 'No, I can't bowl' at a time when he needed me to."
In June, after another failed attempt at a comeback at the start of the T20 season, Garton went for another set of tests. "I had CT scans, where they inject you with metal and check your heart and lungs for blood clots. They all came back clear again." That should have been a positive, but it was hard for Garton to marry his fatigue with the reality that "it was my brain telling my body that there was something wrong".
Then he visited a leading sports cardiologist, Professor Sanjay Sharma in London. Sharma reassured him that his actual fitness levels were "still pretty good" and instructed him to try and keep his heart rate between 120 and 175bpm while training. "He said if I went over 175, I would cook myself, and when I went back to Sussex I found that my heart rate in games had been going up past 200."
After two weeks of training, Garton suddenly felt like his old self again. "It's like someone, somewhere had a dampener collar on me and they thought, 'Oh, he's suffered enough now. After six months, we'll just take it off.' And they just flicked a switch, and I woke up and felt miles better."
We are speaking at the Ageas Bowl, a couple of hours before this season's opening match of the Hundred between Southern Brave and Welsh Fire. Brave win convincingly, chasing down a target of 108 with 31 balls to spare, but Garton's only involvement is to run the drinks. This is another challenge that he has had to contend with: after struggling through the last six months, his performances have understandably dipped. Even so, he is thankful: "Touch wood, I feel like I'm through the other side." On Wednesday this week, he got his first game, returning figures of 0 for 43 off 15 balls in a match Southern Brave lost by a big margin.
He is grateful, too, that Rob Key, the ECB's managing director of men's cricket, rang him before England selected their squad for their ODI series in the Netherlands in June, explaining that they hadn't forgotten about him but wanted him to be "fit and firing again".
He did feel fully fit for the final four games of Sussex's Blast season but conceded 67 runs across five wicketless overs (though he did score 99 runs at a strike rate of 190). The day before the start of the Hundred, Brave's bowling coach, Graeme "Pop" Welch, took Garton to one side after seeing him frustrated during a nets session.
"He said, 'What are you doing?' and I said, 'What do you mean?' He just said, 'Why are you putting so pressure on yourself? You've hardly bowled, you've hardly trained for six months. You're not gonna be perfect straightaway. Don't have any expectations. Go out, have fun. We know how good you are. You're here for a reason.' It was a little bit of a light bulb moment for me.
"I realised that I can look at it one of two ways. Either 'Crap, I haven't trained, and there's so much pressure on me to do well', or 'Actually, I haven't been able to train as much as I'd have liked so I can go out and enjoy myself.' Weirdly, I think I've got less expectation of myself this year because of everything that's happened before.
"I've missed playing. I've missed being around the team, enjoying everyone else's successes - hopefully as well as my own. I have the best job in the world to go out and play cricket and then entertain people. I don't want to think about things too much. I want to go out and have as much fun as possible and hopefully win as many games as possible."