Top secret design for HMS 'Habbakuk' (centre), a giant aircraft-carrier built of ice and wood pulp, which was proposed as a secret weapon in the Second World War. This project was put forward by Geoffrey Pyke in 1942, but was never built as the practicalities involved were too much for the British war effort. The 'Habbakuk' is shown next to HMS 'Indefatigable' (right), a large British aircraft-carrier built of conventional materials.