When the definitive history of the “war on terror “ is written, the complicity of European countries in America’s more extreme enterprises will be one of the sadder chapters. Illegal detention, “extraordinary rendition”, torture and perhaps even murder will headline the charges brought against nations that, until the Twin Towers fell, would have sworn they knew better.

John le Carré examines this toxic collusion in his powerful new novel, A Most Wanted Man. Set in Hamburg, where Mohamed Atta and several of his cohorts planned the 9/11 attacks, it opens with a common sight in “Old Europe” — the arrival of a gaunt, haunted refugee. His name is Issa Karpov, and he is the bastard son of a corrupt Russian colonel and the Chechen woman with whom he fell in love after he raped her (and who was subsequently murdered by her disgraced family).

But Issa is no penniless wretch looking for work at the bottom end of the service industry. The threadbare leather purse he wears around his neck contains the code to a secret bank account established by his now-dead father. Uncertain how to proceed, Issa contacts Annabel Richter, a young German lawyer who works for a foundation that aids displaced persons. She in turn approaches Tommy Brue, the 60-year-old Scottish director of the private bank where Colonel Karpov’s loot is stashed, looking not so much for access to the funds but rather for a benefactor who can help Issa recover from the torture he suffered in Turkish and Russian prisons.

Things get complicated when it emerges that Issa is implicated in attacks by radical Islamic groups. This puts him on the radar of the German security services, who place a grizzled veteran spy named Gunther Bachmann on his case. Bachmann, who adheres to the quaint view that espionage is about gathering information rather than crushing bones, soon suspects the young man’s confessions were simply a means of getting his jailers to loosen the thumbscrews. His superiors do not buy it. Eager to curry favour with their American masters, they see Issa and his new-found wealth as a means of entrapping Dr Abdullah, a charismatic fundraiser for Muslim charities who may be guilty of letting a few pennies of every pound he raises slip into the wrong hands.

As ever, le Carré builds his story’s considerable suspense on character, not fervid action. Issa is a particularly fine creation, a brilliant and promising boy whose mind has been damaged, but not broken, by his terrible past. Bachmann is also well portrayed, an ironic, world-weary survivor of battles both internal and external whose apparent amorality hides the book’s most principled soul.

Centre stage, however, belongs to Brue and Annabel, products of privileged backgrounds who find themselves powerfully drawn to Issa. Brue sees himself as a member of a “dying species . . . salt of the earth, good man on a dark night, no high flyer but all the better for it, first-rate wife, marvellous value at the dinner table, and plays a decent game of golf”.

But it’s a sham, his wealth founded partly on unholy alliances with Russian gangsters and British intelligence. In Annabel, he sees the chance to find some late-innings redemption. For her part, Annabel understands that Issa’s case exists in a netherworld beyond the law, where affidavits and motions are not worth the paper they are printed on. “I knew that this was where the system stops,” she claims, “that this was the unsavable life I must save.”

But in the never-ending war on terror, there is no room for the humanity of Brue and Annabel, of Bachmann and Issa. If the Germans and British don’t sink quite as low as the Americans in dealing with the refugee, it is simply a question of nerve, not principle. Some readers might feel that the bleakness on display in A Most Wanted Man is a long way from the nuanced world of Smiley and his circus. Perhaps, though, this is no criticism of le Carré, whose narrative power and abiding humanity remain intact as he nears his 80th birthday. It is, instead, an indictment of the governments we allow to act in our names.

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