It was discovered, however, that the walls of the barracks consisted of an outer and inner casing, each a foot thick, and built of large sun-dried bricks, the space between being filled up with a mixture of rubble, mortar, and earth, and a few larger stones. This was in the bottom storey. Above that the construction of the wall changed to two thicknesses of lath and plaster attached to either side of a timber framing, and the thickness of the wall diminished to only nine inches. The total width of the wall below was five feet; therefore the lockers in the upper room were immediately above the rubble core of the heavier wall. It would thus be possible to get down through the lockers and sink a shaft through the rubble to a trifle below the level of the ground, and from there to break through the inner casing and come into the empty space below the ground-floor. Work was commenced in the middle of February 1918. For the next few weeks an officer was usually to be seen lolling about at either end of the first-floor rooms, and, on the approach of an interpreter or other intruder, would stroll leisurely down the passage, whistling the latest ragtime melody. Within the room all would now be silent; but when the coast was again clear there could perhaps be seen in the barrack room a pair of weird figures, strangely garbed and white with dust. Somewhere in the line of lockers was the entrance to the shaft-head. The locker doors being only a foot square were too small to admit a man, and so the top planks at the place where we wished to work had been levered up and fitted with hinges to form a larger entrance. To give additional room inside, the partition between two consecutive lockers was also removed; the floor of one locker and the joists supporting the platform at this point were then cut away, and we were free to commence the shaft. For this job six officers were chosen, of whom three belonged to our escape party. The six were divided into three reliefs, and each worked for two hours at a time. The hole was of necessity only just large enough for one man to work there, so of the pair one did the digging, while his partner, when the shaft had progressed a little, sat inside the locker at the top of the hole. When actually at work, the time went quickly enough; but sitting in the locker was very wearisome, as one's only duties were to pass on the alarm when the ragtime was whistled, and from time to time to draw up by a rope the small sacks filled by the digger. When all the available sacks were full, work was stopped, and the two would emerge from the locker. The sacks of rubbish were then carried a few yards along the room and emptied into a space underneath some planks which had been loosened in the platform. At the end of their relief, the two would go off to change their clothes, leaving the work to be continued by the next pair.