Lee-Ann Bell spent her 21st birthday in prison. Six years later, she is serving up gourmet breakfast rolls and barista coffee to the people of Partick, quietly celebrating a different anniversary - she's been clean for exactly one year.

The 27 year old began her drink habit at 13, in the chaos of a troubled childhood and soon after she was on drugs: "heroin, hash, anything". She ended up in Cornton Vale.

Attempts at rehab failed. "They helped you get clean but didn't help you stay clean", she says.

That was before she got involve with Braveheart Industries, the social enterprise launched by Police Scotland's pioneering Violence Reduction Unit (VRU).

She works in their Street and Arrow food truck, permanently sited in Mansfield Park in Glasgow's West End, along with five other ex-offenders, a chef who has worked with Gordon Ramsay and Andrew Fairlie and a "navigator" - a mentor who knows the path of drink, drugs and crime well enough himself.

The term "navigator" is a nod to the project's inspiration, the LA-based Homeboy Industries which has built up a wide range of social businesses run by ex-offenders and gang members, including a bakery and a branded leisurewear range.

Here, it is James Docherty's job to provide mentoring and support to the crew of the US-style food truck, as it dishes up gourmet bacon sarnies (with avocado, rocket and sriracha chili sauce).

"I was in care from 15 and spent about six years in jail for stealing cars, and other crimes of dishonesty and violence," the 39 year old explains. "My last conviction was 15 years ago, but I couldn't find work because of my record."

Now he has a job mentoring and inspiring others like him. But it's a 24 hour commitment, being on hand for participants when abstinence - which all Street and Arrow workers must sign up for - becomes a challenge. "Violence is not a 9-5 job. We are there any time they want, if they have broken up with their girlfriend, say and are bent out of shape and about to hit the pub."

There are many other supports too, including near round-the-clock access to a psychotherapist. Recruits all have troubled and traumatic backgrounds, which they are encouraged to confront.

Inspector Iain Murray, officially Project Lead on Desistance Through Employability at the VRU, says the project has an 80 per cent success rate of keeping people in employment, away from crime and clean and sober. That compares very well with other rehabilitation approaches, and he's been accused of cherry-picking the candidates.

"I do cherry pick," he admits. "I have chosen the most difficult cases, people furthest from the job market. There's no value in doing it any other way."

Although the model is LA's Homeboy Industries, the US version has no police involvement. "I think we're the only police force in the world delivering this form of rehab as a social enterprise," he adds.

Giving people a job and a structure to their days is crucial, but only part of what Street and Arrow does. Most participants lack a positive male role model, Mr Murray says, and need to understand what triggers their criminality or violence and reprogramme themselves. For some it is the first job they have ever had, for most it is the longest lasting, even though contracts are only 12 months. "As well as an SVQ in catering they get barista training, health and hygiene, first aid. They needn't just end up working in catering."

As important is learning to deal with workplace routine, pressures and friction. "Sometimes it's just about giving them a cuddle. They are all used to criticism of their character and actions. But a 'well done'? That's something some of them have never heard," Mr Murray adds.

Chef Kevin O'Hagan is one of those dishing out the praise. He has worked in top restaurants across Glasgow - the Rogano, No 15, Gordon Ramsay's venture Amaryllis, and around the world. After his mother became ill he returned from Dominica bringing a beach food ethos with him and did not fancy a return to standard restaurants. Now he's passing on his skills in a way that feels useful, he says. And he has no doubt about the abilities of his crew. "These guys could hold their own in any kitchen," he says.

While still to prove itself as a viable business and demonstrate its long term impact, the project received £208,000 start up funding from the Scottish Government, with justice secretary Michael Matheson an enthusiast. "The VRU looks at evidence-based ideas from around the world and this is one that works. It is providing people with the skills and opportunity to move into a life free of crime and in employment and the success rate so far is very high. I am keen to see them roll this out across Scotland," Mr Matheson says.

For Lee-Ann the impact is simple. It has changed her life, she says. When the public asks, workers are up front about their past and how they became involved. "People think it s a brilliant idea, and that it should be in more places," she says.

"For me, I have my house now, I pay my way. Bills and council tax were alien to me. I know I've earned this money honestly, - it was always dishonest before. It finally feels like I'm doing stuff right and I'm not used to that at all."