The area is not just open desert. There are large urban centres and the hon. Gentleman will know how difficult it was to stop smuggling in Berlin. It is not easy. The material goes down inside one house and emerges up through another house. It is very difficult to stop, and we have talked to the Egyptians about how they might control it. The best suggestion that I have heard so far is for a 20 ft deep trench on each side of the border. That would probably uncover about 50 tunnels.