Len Deighton is the Flaubert of contemporary thriller writers. He takes enormous, almost obsessional care to get the background to his books exactly right, and he chooses increasingly complicated backgrounds; with the result that, as with Flaubert, our attention is constantly distracted from the story and the principal participants by our admiration for, or perhaps our doubts about, the incidental details. When the background is a Britain which has been under Nazi occupation for a year, a very strong story line, or exceptional characterization, would be required to prevent the reader from focusing on that background rather than on the story that Mr Deighton has to tell. That is why, although SS GB is quite the most interesting book he has written, it cannot be judged his best.

The work exists on two levels of fantasy. One is the counterfactual situation of London in 1941….

[This] is presented convincingly. There can be little doubt that this is much the way things would have turned out if the Germans had won the war in 1940. The narrative is full of nice touches: the German army bands playing "Greensleeves" and "D'ye ken John Peel"; the Dorechester in ruins but able to open a few rooms for American visitors; London full of Wehrmacht personnel on leave, buying up antiques at knock-down prices….

On this level of imaginative creation Mr Deighton is so good that the second level, the plot itself, seems by comparison unnecessarily silly and confused. It revolves round a plan by the Resistance not only to steal the details of an atomic bomb and smuggle them to America, but to do the same with the person of the King. The result is as complicated as it is improbable. There is little point in building up so credible a background if we are then to be told quite so far-fetched a story….

After the first few chapters one has to choose either to ignore the story line altogether and concentrate on learning more about Britain as it might have been under German occupation, or simply to take the book as a moderately enjoyable thriller to be discarded at the end of the journey. This is a pity. If Mr Deighton had not tried to do quite so much, he might have achieved a great deal more.