I need hardly mention that we made the utmost efforts to find the entrance to this passage. Unfortunately, we could work only a very short time each day in the cellar of the clock-tower, for close to the stairs which led to it was the switchboard for the alarm siren and for the electric-light which was used both day and night. Nevertheless, with the help of a large pocket-knife we succeeded after about a fortnight's hard work in cutting a brick out of the wall undamaged. Once this beginning had been made the work of cutting out more bricks went quicker. Then we burrowed farther with the little chisel I had appropriated. The rubble thus produced was wrapped up in newspapers and carried away afterwards. A few officers, of course, always kept 'Cave' above, and whenever the signal agreed upon was given, the bricks were quickly replaced, and then no one could see from the stairs that anything had been going on here. Twice we were surprised. In our extremity all we could do was to flatten ourselves against the wall, and the sergeant who had been to the switchboard went away without noticing anything. After several weeks' work we had cut a hole about a yard and a half deep in the wall. It looked as if we should never get through. To our joy we noticed however, that the wall, when tapped with the chisel, gave a much more hollow sound now. Did this mean that we were near the underground passage? With throbbing hearts we worked on. In three or four days we reckoned we ought to be through. Then the unexpected happened. Next morning, before we went down to the cellar, we noticed to our horror a couple of locksmiths, under the personal direction of the commandant, putting a lock and also a heavy padlock on the little tower door. Our plan was discovered. How, I have never been able to find out. All I know is that the English, in their zeal, made a stupid mistake, for if they had waited until the afternoon they would have caught us going down.