The Trinity Six, By Charles Cumming

Was there a sixth member of the notorious Cambridge spy ring? The answer to this question is vouchsafed us by Charles Cumming, but only in fictional form. However, such is Cumming's persuasiveness, we find ourselves believing that the revelations detailed in The Trinity Six are the real deal.

In 1992, the 76-year-old career diplomat Edward Crane is declared dead in a London hospital. Then 15 years pass and Sam Gaddis, an academic living beyond his means, is enlisted by a female journalist to look into the mystery surrounding a possible sixth member of the Trinity College spy cell. Sam's pleasure at this change in his luck is not to last. His journalist friend suddenly dies, apparently of a heart attack. Sam continues to dig into the secrets of the past, and shadows a man who has said he knows the truth about Edward Crane. Sam is to discover that many individuals with malign agendas - in both East and West - have reason to keep buried certain secrets which turn out to be a threat both to Sam's life and to political stability.

With A Spy by Nature and The Hidden Man, Cumming confidently reminded readers that the literary spy novel was still a genre with much to offer. Both books traded in the betrayals and dissemblings of the field, and their characterisation at times approached the richness of an earlier generation. The Hidden Man dealt with difficult relations between fathers and sons (a recurrent theme, of course, in John le Carré), while A Spy by Nature was a disquieting study of young MI6 operative Alec (the name a nod to Le Carré's ill-fated Alec Leamas ). Accomplished though he was, Cumming clearly had to move out from beneath the senior writer's shadow.

His new book demonstrates he has done just that. The most surprising thing about The Trinity Six is not how splendidly written it is, but that the author himself is so young. Cumming was born in 1971, but appears to have arrived kitted out with the baggage of a middle-aged career spook.

Sam is a memorable creation: unworldly, disorganised, yet tenacious in the face of unpleasant opponents. Cumming's other key character is a terrifyingly on-the-nail female spook, proof that (like his mentor) he writes bloody good women. It would be intriguing to know what the creator of George Smiley thinks of Cumming's career. Le Carré's own son, Nick Harkaway, writes a very different kind of book from those of his father. From a literary point of view, Cumming is a closer genetic match.