If you were asked to imagine the precise opposite of exchanging machine gun fire with the Taliban in the torrid white wastes of southern Afghanistan, what would enter your mind?

How about meditating on a yin and yang symbol while embracing spiritual quietude in the lush, verdant mountains of subtropical China?

One former Lance Corporal in the Parachute Regiment, Keith Abraham, 32, doesn’t need to imagine the contrast.

“Helmand was like a Hollywood war movie,” he says.

“It was both the best of times and the most terrible of times – I met the greatest people in the world there, but I also had to deal with the shock of a good few of them dying.”

Keith served for nearly nine years in the army, fulfilling his lifelong dream to “be in a war”.

“I had a lot of anger, a lot of frustration – I had a thirst for violence and aggression.”

But the trauma of conflict ultimately sucked that thirst out of Keith, and he called time on soldiering to move to the City.

“I walked out of the Paras on the Friday and into [banking company] JP Morgan on the Monday.

“I went from one intense and stressful job to another – until I learned about tai chi.”

A colleague recommended a video of the ancient martial art, and Keith gradually came around to its philosophy of inner peace and non-violence.

“It brought about a profound change in my character.

“It was a central part of my healing process – for me, overcoming what had happened during the war.

“But it isn’t just for people like me – everyone has trauma, everyone has pain, and everyone can work through it.”

A few years after seeing that first video, Keith was in Yangshuo, China, being tutored by Master Wang Zhi Ping in preparation for becoming an instructor himself.

And now he has begun hosting his own classes, at St Margaret’s Church in Canning Town, having quit his job at the bank to devote himself wholly to tai chi.

“It’s a bit scary, financially – I was very comfortable before.

“But I couldn’t deny myself happiness anymore – and now I’m healthier, I look better, I feel better. I had to follow my heart.”

If you are interested in learning tai chi with Keith, visit playfuldragonstaichi.com