Jack Leach has admitted that he feared being derided as "a chucker" after England's internal tests revealed a kink in his action that made his bowling illegal.

He has bounced back so successfully that, barely three months later, he is about to join England Lions on a tour of Sri Lanka, confident that remedial work has addressed the idiosyncrasy in his action that briefly threatened to derail his career.

Leach's left-arm spin was discovered to be illegal during routine tests at the national performance centre in Loughborough. He was on holiday in Portugal in October when Andy Flower, the England Lions coach, phoned him with the news.

As soon as he returned to England, Leach's priority was to rebuild his action with the help of Peter Such, England's spin bowling coach, at Loughborough, and the Somerset bowling coach, Jason Kerr.

"I was shocked," Leach said. "It was bizarre. It was never something that had been brought up before. It has never been an issue in games. I have never been called by an umpire, so it was a totally new thing for me.

"It is natural to be a bit worried and think how big a thing this is, but very quickly I have learned that this is a very small technical thing. It seems a big thing because it is illegal - the whole 'chucking it' tag that goes with it, I don't like that."

For the first time, Leach gave details of the issues that he has had to solve. He explained that the malfunction occurred very early in his action, so making a solution far less demanding than if he had been throwing the ball closer to the point of release.

"Bespectacled and slightly ungainly off the field, Leach was transformed into a smooth and rhythmical figure the minute the ball came into his hands"

"It was just a question of body position," he said. "My arm went quite far behind me, which, at shoulder height, meant that there was a bit of a bend. Then, when I release it, I am dead straight, so it was just a question of taking my arm on a smoother path - one circle rather than going two circles. It is more efficient, so it is a good process for me to go through with my bowling.

"It feels great now. It feels nicer probably. Like anything, it is just a case of grooving it. I have done a lot of hard work to make it a natural thing so I don't have to be thinking about it. I want to be thinking about getting a batter out and so I have done a lot of mirror work to start with, and then bowling from standing. You gradually work your way back and then it's just repetition of learning that new pathway."

Leach's action had never invited the slightest concern during his career, not even in a golden summer in 2016 when he shot to prominence with 65 Championship wickets at 21.88 in a season in which Somerset came close to winning the title for the first time. Bespectacled and slightly ungainly off the field, he was transformed into a smooth and rhythmical figure the minute the ball came into his hands.

He was widely advanced as an England spinner in India. Chris Rogers, the former Australia batsman and his captain at Somerset, had counselled against it, even as he destroyed Yorkshire at Headingley, suggesting "emotionally he still has a bit of a way to go".

Rogers' observation must have been in the selectors' mind when they excluded Leach from the squad. Those same doubts must have resurfaced, too, in October, when he faced the biggest challenge of his career. It is heartening, therefore, that he has met his difficulties with such resolve. It might even be the making of him.

"These things are here to challenge you," he said. "You have to work hard and make those changes. That's what I have tried to do. I am better for going through the process. I know so much more about myself and my action. I have tried to see it as a positive thing."

Jack Leach claimed six second-innings wickets to finish off Warwickshire at Taunton Getty Images

An understandable wish to allow Leach to carry out his remedial work away from the glare of publicity led the ECB, with the misguided secrecy that characterises their approach at a high level, to be evasive about why he was not called to India as a replacement for the injured Zafar Ansari for the final two Tests. The attraction of another specialist spinner was evident, but at the time, Leach was still rebuilding his action from a standing start.

Such was the low-level nature of his fault that it would have been better to shout it from the rooftops. Instead, when the revelations leaked out, they were met with general disbelief.

"It is odd," he said. "I have had conversations with a lot of people and they all say that - that they didn't see it coming. I don't want to be thought of as a cheat."

He prefers not to discuss how far over the 15-degree limit he was, but it was by a substantial margin. "I don't really want to go into that. I was considerably over before and I'm considerably under now.

"I knew it was something I had to put right if I was hopefully going to go on to higher honours, and so it was important to make the change, not just so I am not technically throwing it, but so I am going to become a better bowler as well. Now what's nice is, I know I am well under the 15 degrees and I can focus on being a better bowler the whole time, rather than think about my action in my practice."

The fear for any orthodox spinner found to be breaking the 15-degree limit - a degree of tolerance pragmatically chosen because nearly every bowler straightens their arm at the point of delivery, but it is only beyond 15 degrees that a throw is noticeable to the naked eye - is that the newly modelled action will lose its effectiveness.

"He explained that the malfunction occurred very early in his action, which made a solution far less demanding than if he had been throwing the ball closer to the point of release"

Leach is about to gain early indications of that in Sri Lanka when he returns to match action for the first time in two four-day games, but the nature of the problem he has now addressed suggests he should not be in danger of losing revs on the ball.

"From the bowling I've done since it's happened, I'm still spinning the ball and hitting good areas, so that's obviously what I want to be doing.

"I think it is a little bit unusual in that it wasn't something that was helping me. It wasn't as if I was bowling doosras and that kind of thing. It was technically that, with the way the rule is, it is the difference of the angle between shoulder height and when you release it.

"That was the issue, rather than getting further into my action and giving it an extra flick or bowling doosras. Just another little technical thing that meant I needed to make a change."

A Lions tour, under the captaincy of Keaton Jennings, has come at a good time. Leach has never played in South Asia and he can anticipate the chance to test his action on encouraging pitches in unpressurised circumstances before returning to Taunton to prepare for the start of the county season in mid-April.

"I am really happy to have been picked on the tour," he said. "I'm looking forward to going out and trying to win games for England Lions, to getting back to bowling, playing cricket and enjoying the contest rather than talking about technical things."