The last untold story of the First World War: the fortunes and fates of 170,000 British soldiers captured by the enemy.

On capture, British officers and men were routinely told by the Germans 'For you the war is over'. Nothing could be further from the truth. British Prisoners of War merely exchanged one barbed-wire battleground for another.

In the camps the war was eternal. There was the war against the German military, fought with everything from taunting humour to outright sabotage, with a literal spanner put in the works of the factories and salt mines prisoners were forced to slave in. British PoWs also fought a valiant war against the conditions in which they were mired. They battled starvation, disease, Prussian cruelties, boredom, and their own inner demons. And, of course, they escaped. Then escaped again. No less than 29 officers at Holzminden camp in 1918 burrowed their way out via a tunnel (dug with a chisel and trowel) in the Great Escape of the Great War.

It was war with heart-breaking consequences: more than 12,000 PoWs died, many of them murdered, to be buried in shallow unmarked graves.

Using contemporary records - from prisoners' diaries to letters home to poetry - John Lewis-Stempel reveals the death, life and, above all, the glory of Britain's warriors behind the wire. For it was in the PoW camps, far from the blasted trenches, that the true spirit of the Tommy was exemplified.