This took place the day before the German prisoners escaped. These boys were, in fact, observed, but so large was the aerodrome that they were able to do a certain amount of damage before being approached. They then got away, but were apprehended afterwards. Some of our bomber aerodromes are twice the size of Hyde Park, and it is impossible to prevent an occasional snooper from getting into so large an area. But, as regards sabotage, there has not been a single case since the war began. Sabotage can be done on a dangerous scale only by a considerable organisation, and we have our own methods of preventing it.