For the best part of three decades, Jean-Marie Roughol lived as a down-and-out in Paris. Begging in the shadow of the Arc de Triomphe, he was a familiar figure to the wealthy and famous who frequented the designer boutiques and luxury convenience stores of the Champs Élysées.

Some ignored his polite appeals, scurrying past and looking the other way; others stumped up a coin or two – or even a note; and a couple of people offered him walk-on parts in their movies.

Now, following a chance encounter with a former government minister who helped Roughol publish an account of his years living rough, his life has undergone what he describes as a “miraculous” transformation.

Royalties from his book, which has sold 50,000 copies and is No 3 in Amazon’s list of “French society” bestsellers, mean Roughol can afford his own flat, is looking for a job and is already writing a sequel.

“I have been given a chance in life. It’s a miracle for me and I have no desire to go back to the street. I don’t want to disappoint the people who have helped me and believed in me,” Roughol told the Observer. “I’m going to find a job, even if it’s washing up in a restaurant. Now it’s my turn to help people in the street. Anyone can find themselves down and out. You can be an executive and lose your job, or suffer a fire or a catastrophe, or have a tiny pension you can’t live on and suddenly, there you are. And those who are not on the streets have to learn more solidarity because it could easily be them.”

“I do not feel that I have seen more than the fringe of poverty,” George Orwell wrote in Down and Out in Paris and London more than 80 years ago. “Still, I can point to one or two things I have definitely learned by being hard up. I shall never again think that all tramps are drunken scoundrels, nor expect a beggar to be grateful when I give him a penny, nor be surprised if men out of work lack energy, nor subscribe to the Salvation Army, nor pawn my clothes, nor enjoy a meal at a smart restaurant. That is a beginning.”

Roughol, 48, is no Orwell. But his account of life on the French capital’s streets, Je tape la manche (I’m begging), shows that little has changed for those living life on the street.

Jean-Louis Debré, the former president of the constitutional council, with Jean-Marie Roughol. Photograph: Bertrand Rindoff Petroff/Getty Images

“I never imagined that my career would be begging in the streets of Paris, to beg to live, to survive,” Roughol writes. “I never thought I’d have to sleep at night in the street, in staircases in the metro … of course, I’m responsible for what happened to me, but my life didn’t begin well. This isn’t an excuse: it’s a fact.”

Born in Paris a month before the student uprisings of May 1968, Roughol’s mother abandoned him and his father sent him to foster parents in the country. On the train, he writes: “I was happy, I was convinced I’d see elephants. I kept looking out of the window for them.”

The young Roughol’s disappointment was not confined to the lack of elephants in rural France. His foster mother was cruel and violent, gave him stale bread and water, and locked him in a pitch-black cellar, he says. “There were no presents, no love, no food; these people were paid to raise children so I was just an income for them.”

Even when his father eventually brought him back to Paris, Roughol’s adolescence remained chaotic. He dropped out of school, repeatedly ran away from home and, by the age of 20, after episodes of petty delinquency and a brief stint of military service, was already adept at living rough.

He recounts how he spent the night in metro tunnels with “rats the size of cats”, sometimes getting up to find his meagre belongings, “my backpack and even shoes”, had been stolen.

Roughol’s life changed after he offered to look after a bicycle belonging to Jean-Louis Debré, 72, a former government minister, on the Champs Élysées. After the pair chatted, Debré befriended Roughol and encouraged him to write down his experiences.

In between begging, Roughol sat in the local park jotting his recollections in notebooks, which he handed over to Debré to edit. When he pointed out he had little formal education, Debré advised him not to worry about his spelling or grammar but just “write”.

“I told him the rest wasn’t important and I wanted to understand his life, why he begged,” Debré explains in the book’s preface. “Why are only certain celebrities or those who claim to be, politicians, stars of television, radio, cinema, allowed to reveal their past, write or have their autobiography edited? Do those who are anonymous not have something interesting to say? He [Roughol] teaches me more than I offer him.”

The book was published in 2015, but it was not until a few months ago that Roughol received a royalties cheque, enabling him to start his new life. The paperback came out in November.

Today, Roughol hails Debré as his saviour. “Two years ago, I could never have imagined being where I am now. Jean-Louis is the father I never had. He still rings me often and hasn’t dropped me. He said my life had started to rise and now I’m on my feet it’s up to me to make sure it continues. He’s right,” Roughol says.

Roughol made his New Year resolution some time ago. It was never to return to the streets. He intends to keep it.