Recent literature has been full of “what-iffery” writing about the possible dystopian results of a German victory in the Second World War. From Martin Amis to Robert Harris, this is a well-trodden path, and, it has to be conceded, not one that wins universal applause.

Now it is the turn of the best-selling historical novelist C J Sansom, whose Shardlake thriller series, set in 14th- and 15th-century England, has won a devoted following — and may, indeed, fill that Hilary Mantel-shaped hole in one’s reading while waiting for her next book.

Sansom has also written a well-received stand-alone novel, Winter in Madrid, about the Spanish Civil War. In the latest, Dominion (Mantle Books, £18.99), he abandons, to some extent, his quest for recreating a historically accurate world and instead offers a parallel universe, full of fog and mystery.

The book opens in 1952 in a Britain that has lost a war with Germany which lasted a scant year from 1939 to 1940. Only France and Britain continue to have a Jewish community; all other Jews in Europe have been swept away to the east, there to perish in Nazi gas ovens. Britain’s Jews wear yellow stars and the entire country is fearful of a government led by Lord Beaverbrook, Oswald Mosley, Lloyd George and Enoch Powell.

Churchill is the renegade head of the Resistance movement, never sleeping two nights in the same place. Hitler is dying and the most powerful Nazis are jockeying for position as his successor.
And into this toxic mix the reader is left to wonder: what if? What would the British have done, if its Jews had been marched away for deportation?

Sansom offers a chilling answer with a scene in which rounded-up London Jews are trooped through Tottenham Court Road, guarded by watchful, blackshirted, auxiliary policemen and viewed with smug satisfaction by some, and undisguised horror by others.

The book’s main protagonist, David Fitzgerald, is desperately trying to cover up his own Jewish identity. And on his tail is a crack Gestapo man, flown over from Berlin especially for his expertise in rounding up Jews.
Sansom’s skill is in providing the anxious reader with the conundrum: what would I have done? Or, more generally and dramatically: What if?