The escape signal

Book illustration of the escape signal given by guards of convicts working in the Arsenal, from page 221 of 'The criminal prisons of London and scenes of prison life' by Henry Mayhew and John Binny. The authors describe the scene: "Then we came upon an angle of the arsenal wall against the Plumstead high-road, where we saw an armed guard with his carbine, marching rapidly backward and forward. 'Now I shall know directly whether all is right,' said the governor, as he raised his hand. The sentinel instantly halted, presented arms, then raised his right hand. 'Had there been an escape', continued the governor, 'he would have grasped his carbine by the barrel, and held it aloft horizontally. That is the escape signal, and this man is stationed here because escape would be easy over the wall to the high road. Only the other day I caused a drain to be stopped up that led from the arsenal to the marshes; for we once had a hunt, that lasted all day long, after two prisoners who got into that drain. We caught them at its mouth by the Plumstead road'."