LJ Flanders is only 27, but his life experiences already include a spell in prison, qualifying as a fitness trainer, writing a best-selling book and meeting Prince Charles.

Now, the latest stage of his extraordinary journey sees him back in jail, but this time he’s there for positive reasons, using the power of physical activity and exercise to help those in a situation he knows all too well.

With support from the National Alliance of Sport for the Desistance of Crime (NASDC) and using its recently launched Theory of Change as a guide, LJ has devised a fitness programme for inmates at HMP Wandsworth, spreading the wisdom that helped him turn his life around.

LJ admits he was in a “desperate” state while banged up for 22 hours a day inside HMP Pentonville in 2011. Unable to find any suitable exercise manual, and with no internet and limited access to the gym,  he created his own cell workout routine to keep fit and stop him “climbing the walls”.

He also studied for his qualification as a fitness instructor and, when in his cell, began writing notes and sketching diagrams of his body workouts, all of which were designed for limited space and no equipment.

On his release, the manager of his local Virgin Active gym in Essex “took a chance” on LJ by offering him a job as a fitness instructor.

In the evenings, LJ worked his cell notes and sketches up into a self-published book, Cell Workout. It became so popular, especially among the prison population, that he says “it quickly became the most popular book in every British prison library – and the one most likely to go missing!”

He toured prisons to do Q&As and book signings, then late last year, the book was snapped up by publishers Hodder and Stoughton who turned him into a tabloid star.

Via a grant from the National Offender Management Service (NOMS), support from the Prisoners’ Education Trust, and guidance from the NASDC’s Theory of Change, he has now devised a fitness workshop for inmates at Wandsworth. Other elements structured around it include goal-setting, motivation, relaxation, meditation, education and healthcare. “It’s about encouraging the men to use their time wisely,” says LJ.

The course lasts two weeks for up to 15 men at a time. The response, LJ says, has been “massive – completely unheard of,” with places already booked up until June.

When planning the course, it was vital to ensure it contributed real value to the inmates’ rehabilitation and that it could prove its impact with measurable effects on their engagement, physical and mental wellbeing and individual development. That’s where the Theory of Change came in.

Justin Coleman, Head of the NASDC, explains: “The Theory of Change is our vision for how sport can achieve maximum impact on preventing criminal behaviour and rehabilitating offenders. Using it as a guide, we were able to help LJ formulate his groundbreaking workshops to deliver lasting behaviour change among the inmates at Wandsworth Reform Prison.

“The results of the workshop will form part of our national evidence base to highlight the power of sport and physical activity in reducing crime. Having been there and done it himself, LJ is the perfect example of rehabilitation and we will continue to support and monitor his progress.”

LJ adds: “The Theory of Change is like a business model. It’s like a refined way of goal-setting, drawing a graph for each participant of where they are now, what they want to be when they’re released, and plotting what they have to do in between to make that behavioural change happen.”

Researcher Hannah Baumer is evaluating the impact of LJ’s workshops on behalf of NOMS (pending its approval). She agrees that the Theory of Change is a vital tool for anyone setting up Sport for Development projects.

“It’s like a checklist – you look at what you’ve already got and map it against the Theory of Change to see which areas you have and haven’t addressed,” she says.

“For LJ, the help of Justin and the Alliance has been important too. They were able to provide contacts to help the men carry on achieving their goals once they’re on the outside. Running a two-week course with nothing afterwards is actually more harmful than running no course at all, so that follow-up element is really going to help.”

LJ admits re-entering the prison environment with a radio and set of keys was strange at first, but Wandsworth’s Executive Governor Ian Bickers helped him settle in.

“He told me, ‘You’re not an ex-offender any more, you’re one of us now. You had a number, but you’ve proven and bettered yourself all off your own bat.’ That was great to hear, and I’ve also got the respect of the inmates, because I’ve been in their position too.”

LJ’s meeting with Prince Charles came via the Prince’s Trust, who initially provided a loan after his release to help him publish the book. The Prince told him: “We give people a hand up, not a handout.”

That neatly sums up LJ’s vision for where he wants to take the Cell Workout project next. His long-term plan is to engage other ex-offenders in personal training and spread the delivery of workshops to other reform prisons around the country.

LJ reveals: “My friends and family asked me, ‘Why on earth do you want to go back into prisons?’ But I actually feel obliged to do it. I feel like I have to. I want something positive to come from the mistake I made.

“I believe I can make a difference, give them hope and look towards a brighter future. I tell the inmates that I’m no different from them, but I am very, very determined. There will always be roadblocks, but they should never stop you from achieving.”