The Wooden Horse by Eric Williams

One of the best known WWII PoW escape stories. Threemen, Michael Codnor, Eric Williams and Oliver Philpot made
it back to Britain via the Baltic and Sweden after escaping from Stalag Luft III.
Stalag Luft III was designed to be escape proof. Forty or more tunnels were discovered under construction before this one succeeded.
The tunnel's start point was concealed at a position in view of the camp guards. It was opened only when a vaulting horse was placed over it. The vaulting horse was carried to and from the concealed worksite each day. Inside the horse
were the tunnelers, and, after a day's work, tunnel cuttings.
While they dug, other PoWs used the vaulting horse for its original purpose - physical exercise.