But his recovery occupies only the last few pages. Most of the book is about the drugs, prison, the street, and the low-life, criminal, selfish and violent thievery and drug-dealing of his teens and twenties. Quite apart from what he did to himself, there was a baby neglected, relationships sabotaged, chances blown, fellow humans abused. One of the queasiest moments is when his sister invites her wreck of a brother for Christmas, and he takes the opportunity to sell ecstasy and cocaine to her partner's "younger relatives".
I met Mark last week and liked him a lot. Despite his publisher's insistence on selling the book as a "misery memoir", its blurbs majoring on what was done to him rather than what he did, the book itself takes honest responsibility and expresses regret, and the life he leads now is a good making of amends. Mark indeed may end up more valuable to society than a lot of lifelong do-gooders.
Yet there is one bit of his childhood which struck me particularly, and which teachers might note. With a depressed, hopeless mother and a violent father, he never knew normality at home. One day he went to the house of a teacher - Mrs Allbut - and marvelled at the fact that people talked and listened to one another without shouting or hitting. They were even, he says amazedly, listening to other people's conversations on the radio - The Archers was on. And the husband told him he had been "a pleasure" to meet.
Nobody had ever told Mark he was a pleasure.
So I asked him the politically incorrect question. Suppose he had been taken away and fostered or adopted by a family like the Allbuts - gentle, middle-class professionals. Would his life have turned out better? Or was it always best to be with your real mum and dad? His answer was flat.
Better to have been taken away. He used to dream of being put in the local children's home, though the children there envied him having "real"
As for the Allbuts, their memory remained a beacon for him during the worst times. The teacher's family were civilized. They were grown-ups. They were kind to children and to one another. When we have, straight from the horse's mouth, a clear belief that these things outrank the power of the natural genetic family, perhaps we too should listen. And perhaps teachers and heads who see or guess the abominable lives that some of their pupils lead should not only demonstrate the merits of gentleness and civilization, but from time to time barrack social services to be less timid about saying the unsayable: that some parents don't deserve to have their children in their power. Genes aren't everything.