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...