All of England's Test specialists were relieved to arrive back home after 10 weeks in Sri Lanka and India, but none more so than Jack Leach.

Leach lives with Crohn's disease, and his immunosuppressant medication weakens his immune system. As a result, he is more susceptible than most when it comes to illness: he was struck down with gastroenteritis and sepsis on England's 2019-20 tours, and back in the UK, he has had to be particularly vigilant with regards to Covid-related protocols over the last year.

But the end is in sight. After six days of self-isolation on his return home, Leach received the first dose of his Covid vaccine. His second shot is due to be administered in two weeks' time, and he is upbeat about the prospect of an imminent return to something approaching normality.

"I was in straightaway once I'd done the six days," he says. "It went well - I felt fine. It's a relief. I don't think of myself as being more at risk than others, but ultimately, because of the medication I'm on, I am. It's nice to have it done - playing sport, I spend a lot of time around other people, so it will feel nice to have both of them out the way, and hopefully I can crack on a little bit more normally after that.

"I think I got a lot of confidence from the winter in terms of my health, getting through the tours. I've learned over the past couple of years that it's relapsed slightly when I've felt under the extreme stress and pressures of playing international sport - it gets a little bit worse with that. To get through the series has given me a lot of confidence that I can play at this level and that my illness isn't going to hold me back. That's a really great thing to experience."

When Leach flew to Sri Lanka at the start of January, he did so in the knowledge that it was a make-or-break tour for his England career. He had not played a Test in 14 months, and played only two first-class games in 2020 after spending the summer as back-up to Dom Bess in the England bubble: with conditions in his favour, a couple of poor outings would have been a significant setback to his long-term prospects.

Instead, he was one of very few England players to leave Asia with his reputation enhanced. Along with Joe Root and Dom Sibley, Leach was one of three men to play all six Tests of England's winter, and finished as their leading wicket-taker by a long stretch, with 28 scalps at 31.14 apiece. He will start the summer as England's undisputed first-choice spinner, and is relishing the chance to play New Zealand, India and Australia before the end of the year.

"I don't want to be too positive about it after we lost the [India] series 3-1," he reflects. "We had a good win in Sri Lanka, but that was probably when I felt worst - rusty, getting back into things after such a long time not playing. I felt like I got better and better across the six Tests. Going into that first Test in Chennai there were nerves - will you be able to do it against some unbelievable players? - but my confidence and belief improved throughout."

In particular, Leach is proud of how he recovered from the mauling he suffered at the hands of Rishabh Pant. His first eight overs in India cost an eye-watering 77 runs as Pant lived by the sword, hitting with the spin and out of the rough outside his off stump in an attempt to blitz India back into the game, but Leach's figures - and confidence - recovered from an early dent as he spun England to victory with four second-innings wickets.

"Eight overs for 80-odd, smashed everywhere," he laughs. "I'd be lying if I said I was feeling really positive at that time. That moment taught me a lot about myself. There were a couple of sixes that only just went over fielders and looking back, he probably felt more at risk when he was defending. He didn't play with any kind of fear: he came hard, and fair play to him.

"It taught me that when someone is showing no fear, it's important to match that back at him, in terms of how we feel when you bowl. That was a really valuable experience, and one that I'll look back on and think helped me a lot. I felt like I had nothing to lose after that moment. I came back strong and felt like I got better and better through what I learned.

"I just want to take it a day at a time, and trying to see every time I'm on the pitch as a chance to do well and to learn. That's what I was missing in my life for the 18 months before. I hadn't played much cricket and with that, I lost a lot of confidence and didn't feel like I was doing what I'd been doing for years before that: bowling spin, trying to take wickets and influence games. That's what brings the best out in me. Now I just want to experience as much cricket as possible, whether that be for Somerset, for England, for Taunton Deane - whoever."

The result is that Leach goes into the County Championship season feeling as confident as he ever has in his own ability. He will play up to seven games for Somerset at the start of the season before linking up with the England squad before the first Test against New Zealand, and the club are delighted to have him back, with captain Tom Abell describing him as "one of the best spinners in the world".

Following Bess' departure to Yorkshire, Leach has extra responsibility within the squad, but has a refreshingly relaxed outlook on the season ahead. He is hopeful that he will be able to play some part in the Royal London Cup before the Tests against India - he has not played a List A game since 2016, and spoke to Moeen Ali over the winter about the benefits white-ball bowling might have on his Test game - and the Championship's schedule should allow him to play a major part in Somerset's title push.

"If anything, I feel less pressure coming into this season than I have before," he says. "I feel like I've bowled how I've wanted, and with the confidence I've gained from that, I've learned a lot. When your confidence is low and your ego has taken a bit of a hit, you can become a bit closed off from learning. For me, that confidence has made me want to learn more and more, and get better every day.

"Before, I was trying to rip up what I'd done one day and trying to become a different bowler the next day. I'm always trying to get better but I think I do it in a much healthier way now, trying to get 1% better every day. I think those six Tests have given me the confidence that I'm a good bowler and if I add to that slowly, I'll improve quicker than I would if I was trying to make big changes overnight."

Matt Roller is an assistant editor at ESPNcricinfo. @mroller98