One photograph titled ‘Wanted ... for trial’. Caption on the back reads: ‘… Not a killer. Just assistant experimental officer Leslie Harrow with one of the latest models of explosive driver. It came from Switzerland. Is used for driving studs, nails and the like into brickwork and concrete. It’s one of the aids to speedier building being tried out at the Department of Scientific and Industrial Research. The Thatched Cottage, Barnet.’