Sir John Mills resembled Colditz prisoner Mike Sinclair, alias The Red Fox. Sinclair escaped from Colditz three times. His final attempt ended in tragedy when sentries killed him on September 25, 1944. A portrait of Sinclair, drawn by John Watton, appears in "Men of Colditz" by P.R. Reid.
According to the epilogue, Lieutenant Colonel Airey Neave, D.S.O., OBE., MC made the first British Home Run in January 1942. Neave later served as a Conservative Member of Parliament from 1953 until he was murdered by the Irish National Liberation Army (INLA) by a car bomb at the Houses of Parliament, on March 30, 1979.
P.R. Reid wrote three books on Colditz: "The Colditz Story" (1952), "The Latter Days at Colditz" (1953), and "Colditz: The Full Story" (1984). The earlier book, based largely on Reid's own experiences, was the basis for this movie.
Colditz Castle is a Renaissance castle in the town of Colditz near Leipzig, Dresden, and Chemnitz, Germany.
The scene where one of the prisoners impersonates a German guard is similar to a real plan that was used by the British. In April 1943, Lieutenant Albert "Mike" Sinclair and Lieutenant "Monty" Bissel approached British escape officer Dick Howe with a novel idea: Sinclair would disguise himself as Stabsfeldwebel Rothenberger, the senior N.C.O. in charge of the nightly inspections on the eastern sentry posts, and would then replace a number of sentries with suitably disguised prisoners. If successful, this would give a (roughly) five minute period during which as many prisoners as possible would try to escape through the now-opened gates. While the men were escaping, Sinclair and his guards would "set off in pursuit" and sow further confusion by ordering the real guards to return to the castle and gather reinforcements. After several months of meticulous preparation, the plan was finally ready to be executed on the evening of September 4th. Sinclair and British Officers John Hyde-Thompson and Lance Pope (both fluent German speakers who would act as the replacement guards) entered the sickbay and climbed out of the specially prepared window and onto the terrace. They rounded the northeastern corner of the terrace and approached the first guard post. Sinclair told the guard that he was relieved of duty and ordered him back to the guardroom. The remaining guards looked askance at each other as "Rothenberger" approached, curious as to why he was conducting his inspection earlier than usual. Up in the sentry box, Sinclair told the guard that there had been an escape attempt on the other side of the castle and ordered him to return to the guard house for further instructions. The guard promptly saluted and marched off, his place taken by Pope. Sinclair then ascended the catwalk above the gate and repeated his orders to the next guard, who then climbed down, his place taken by Hyde-Thompson. Only a single German soldier stood in the way of success. Upon receiving the orders, the sentry answered that he was under strict orders not to leave his post under any circumstances. Sinclair then began shouting at the German who stood his ground and asked to see the Stabsfeldwebel's pass. Despite all of the months of planning, it was discovered the the color of the passes had been changed that same evening and, aware that something was wrong, the guard raised the alarm. Within a few seconds, two further groups of Germans (including the real Rothenberger) converged on the gate. Unwilling to admit defeat, Sinclair continued to abuse the hapless guard, hoping to bully him into obedience. As the additional guards arrived, a scuffle ensued that ended when Sinclair was shot in the chest. He later recovered from his wound while the guard who shot him was quietly transferred to the Eastern Front.