It should be added that—as the barrack was originally built—the far ends of the ground, first, and second floor corridors were exact replicas of the near ends, and gave directly on to the orderlies’ staircase through swing doors. These doors had at the outset been securely boarded up. Early in the history of the camp a trap-door had been made by some officers through the boards on the dining room floor, but it had been discovered by the Germans, who were now on their guard for any repetition of the attempt; so that it was now a physical impossibility to reach the orderlies’ quarters or their staircase by any other means than walking in at the further doorway. Similarly, orderlies could not reach their own quarters except through their own door. From the near door of Kaserne A (the Kommandantur door) to the far (orderlies’) door of Kaserne B was a distance of some 150 or 160 yards and constituted the base of the segment formed by the conformation of the buildings and enclosure. The arc of the segment was represented by the barbed wire fence with its neutral zone which ran from just opposite the orderlies’ door (E)—where it joined the outer wall—round the semi-circular _Spielplatz_ till it merged in the parcel room and guard room opposite the Kommandantur. The space thus enclosed between the base of the segment and the arc represented the gross amount of outdoor elbow room for the inmates of the camp, and measured about 410 yards round. The net available space was much less. One German and two English cook-houses, a twenty-yard square potato patch, a wood shed, cobble-stones, horse troughs, parallel bars, and a cinder path running inside the wire, were factors which considerably reduced our field of sport. Just behind the length of the two Kasernes ran the outer barrier, barbed wire superimposed on iron palings five or six inches apart, with sentries on the inside and later on the outside beat as well. The whole of the ground directly between the two Kasernes, and again between them and the outer barrier, was No Man’s Land and forbidden to the British. If you looked from the whitewashed window at the end of the ground floor corridor in Kaserne B, you saw an eight-foot wall between you and freedom. This wall ran at right angles from the far end of the wired palings and was wired on top. There was a sentry permanently posted at the angle on the inner side, and early in the year the defence was further strengthened by posting an additional sentry outside. This fact had an important bearing on the history of the tunnel. The wall had a postern gate (D) just opposite the orderlies’ entrance. This, of course, was always kept locked. It was in any case impossible to get at without either jumping from the end window of the corridor and braving No Man’s Land, or cutting the wire near its point of junction with the end of the building by the orderlies’ door. ------------------------------------------------------------------------