A 17-year-old boy, thoughtful, studious and gifted, attends a Catholic boarding school in rainswept Carlisle. His sister lives near by and he is with her when a letter arrives from their parents, who live in a logging camp on Vancouver Island, on the far side of the world. The parents have been in a car crash, a head-on collision on the way back from Mass. They are alive. The father is able to write, after all — but only just. He does so with his left hand.

The boy reacts with quiet detachment, or so it might seem to an observer. But he has been raised with religion and has embraced it consciously, and it rescues him. “My first thought,” he says, looking back nearly 30 years later, “was that God is intimately involved in this in some way. It was almost a consolation”.

The boy is not a character from William Brodrick’s haunting first novel. It is William Brodrick, 45, ex-monk, ex-barrister and now the internationally bestselling literary thrillerwriter of The Sixth Lamentation, which tells the stories of an alleged Nazi war criminal claiming sanctuary in an English Catholic priory, and a woman dying of motor neurone disease who alone can prove his guilt.

It has sold a cool 150,000 but is about to sell a great deal more, as it’s been chosen for the Richard & Judy Bookclub on Channel 4, the jackpot for a first-time writer — it can deliver instant authorial stardom. Their attention tends to be lavished on books with bottom; with what your English teacher might have called a strong moral dimension. This one is no exception and Brodrick’s own story is the reason why.

He seems mildly stunned by his success, but, broadly, contented. It was not ever thus. When his parents had their crash, his tribulations, and theirs, were only beginning. Soon afterwards his father suffered a stroke and never walked or talked again. His mother, outwardly, was even more gravely injured, but recovered enough to nurse her husband for 20 more years until he died of cancer. Ten of those years were taken up with a legal battle with the other driver in their collision. They won damages, but only enough to cover their costs, and the real price for Brodrick was a dark depressive cloud over his teens and early twenties.

A year after his father died, his mother contracted motor neuron disease and also died. And not long after that Brodrick, who was then an Augustinian friar, decided against a life in holy orders. He was called to the Bar instead. Then he was hit with his own dose of cancer. He might reasonably have railed at a world that seemed to have turned against him. He actually felt, he says, “spiritual sterility; drained, (with) a gradual realisation that I had a very, very close shave. And there were so many things I’d have wanted to have done”. The unspoken words are: “. . . if I’d died.”

He was unhappy as a lawyer, and a ten-year percolation began. It ended with The Sixth Lamentation, which shines a glaring spotlight on the Catholic Church’s shameful compromises with fascism, but also seems to have brought fulfilment to a man who has risked a lot to find it.

In the flesh, Brodrick cuts a quite unexpected dash. We meet in an opulent Bayswater home that turns out to be his publisher’s. He is dressed immaculately in matching rust- coloured blazer and brogues. He’s quiet and intense, a bit like John Grisham, that other lawyer-writer, but much less self-assured. Small wonder. He has been through enough to break a more fragile psyche into little pieces.

Brodrick’s mother was Dutch, and her extraordinary life — and death — is not just the inspiration for his book but also seems to have made him who he is. The earliest image he saw of her came from an old film taken when she was 16, with her family in Java in 1936 where her father was a colonial military pastor. “Everyone was waving,” Brodrick says. Then Nazism intervened. His mother returned to university in Holland just in time to be trapped there by the outbreak of war, while his grandparents, aunt and uncles were interned in a concentration camp as they refused to take the obligatory oath of loyalty to Hitler.

In Amsterdam, his mother moved in with a prostitute prepared to hide her and joined a group smuggling Jewish children out of occupied Holland to safety. On one run she was caught. A child was taken from her and she was jailed for a year. “She remembers being in Arnhem. She remembers being in trees at night with the children she was helping through the lines.” Brodrick talks in the present tense, relating his one attempt to get his mother to retell the whole thing into a tape recorder. “She remembers hiding under bodies. It was horrific, and this was apart from having been imprisoned and the humiliation she was subjected to, the strip-searching and the violation.”

Released without explanation, she found that year hard enough to recall at the best of times. Then, when struck down by motor neuron disease, the progressive paralysis of her tongue and jaw killed communication even before it killed her.

The effect on her son was devastating and he returns to it frequently. “She died in a way that was shattering for me,” he says, after warning that describing it might choke him up. “I flew from London to Canada and found that she’d just stopped eating. When I arrived she was lying completely still and spoke to me using an alphabet card. She was practically a skeleton at this stage and just waiting to go. She didn’t want me to wait. I don’t think she wanted to be seen stripped down like this. So I had to lean over and just say, ‘well, goodbye’, and get in a taxi. It was a terrible, terrible experience.”

It also shook his faith. He was on an elastic leave of absence from the Augustinian order in which, from his mid-twenties, he had imagined he would spend his life in full-blown monkish abstinence and poverty. Instead, he had been working with homeless people in London and on his way back to them from his dying mother realised “that at that point, intellectually, I simply could not understand God’s relationship with the world”.