Stalag Luft III it as a longer third-person narrative under the title "The Wooden Horse", which was filmed as "The Wooden Horse" in 1950. He included many details omitted in his first book, but changed his name to "Peter Howard", Michael Codner to "John Clinton" and Oliver Philpot to "Philip Rowe". Williams also wrote a prequel, "The Tunnel", an extended study of the mentalities of life as a prisoner of war. Although not an escape novel, it shows the profound urge to escape, and explores the ways that camp life affected men's emotions. Paul Brickhill was an Australian-born Spitfire pilot, shot down in
Bill Ash escape, but the tunnel was discovered when 10 prisoners had got away. Ash continued the attempt and eventually gained his freedom. He boarded a goods train for Kovno, but was discovered by station guards and returned to Sagan. His de-briefing after liberation from captivity in April 1945 records the places where he was imprisoned as Dulag Luft (Oberusel) for about three days in June 1942, then Stalag Luft III at Sagan from June to September 1942 Oflag XXI-B (Schubin), where he was held from September 1942 to April 1943, back to Stalag Luft III for April and May 1943, and