July, 1918. Surrounded by steel palisades and barbed-wire fences, Holzminden was the most heavily guarded POW camp in the world. Patrolled by ferocious dogs and armed guards with orders to shoot to kill, it was a brutal punishment camp, housing 700 prisoners of all nationalities. To escape would take boundless ingenuity and nerves of steel. Many tried. Prisoners used sardine-tin openers to pick locks, forged documents, sent messages using milk as an invisible ink, and created fake uniforms and elaborate disguises - one even impersonated the notorious camp commandant. Every attempt failed, leading only to ever-tighter defences. But on the night of 23 July 1918, twenty-nine undaunted Allied prisoners achieved the impossible. They had spent nine months using knives and spoons to move tonnes of earth, clay and stone, digging a tunnel over 150 feet long through the foundations of the barracks and under the walls and barbed-wire fences, to the farmland beyond. This is the fascinating story of how they did it - and of the many who had failed before them. Neil Hanson provides a rare insight into the minds of these prisoners of war, revealing their resourcefulness, courage and persistence - and inexhaustible good humour.