development of a screw-propelled vehicle based on an old patent called the Armstead snow motor. This consisted of a pair of lightweight cylinders, shaped like very large artillery shells, to support the weight of the vehicle. These cylinders have a spiral flange that digs into the snow; when the cylinders turn (in opposite directions), the vehicle is propelled forwards. Pyke envisaged that a small force of highly mobile soldiers could occupy the attentions of many enemy soldiers who would be required to guard against possible points of attack. Initially, Pyke's idea was rejected. Then, in October 1941, Louis Mountbatten replaced Roger Keyes as Chief of Combined Operations. This changed the character of the department and Mountbatten allowed unusual talents and ideas. Conservative Member of Parliament Leo Amery wrote to Mountbatten recommending that Pyke's Norway scheme, originally rejected by Keyes, be re-examined and that Mountbatten should take Pyke onto his staff. Mountbatten valued Pyke's ideas, and for liberalising other staff, eventually adopted the plan. The scheme became Operation Plough. When presented to Prime Minister Winston Churchill, he noted in the minutes of the meeting: Pyke's snow vehicle project was superseded by Canadian development of the Weasel tracked personnel carrier, produced first for the American-Canadian commando unit the First Special Service Force, which trained first for Norway but was actually deployed in Italy. The US built hundreds of these as the M29 vehicle. Project Habakkuk In April 1942, Pyke was presented with the problem of how to prevent the icing of ships in Arctic waters. He took the problem to Max Perutz at the Cavendish Laboratory, Cambridge; Pyke knew that Perutz had previously worked on the physical properties of snow with regard to the difficulties of Operation Plough. Perutz proposed a solution and in a footnote his memorandum noted that: In September 1942, Pyke sent a 232-page memorandum to Mountbatten detailing his ideas. It suggested a number of uses for ice and for super cooled water (water that has been cooled below its freezing point while remaining liquid) and the suggestion of the construction of gigantic aircraft carriers from ice that was either frozen naturally or artificially. Whereas conventional aircraft carriers were restricted to relatively small, specialised aircraft, these could launch and land conventional fighters and bombers. As such, they could provide air cover for convoys in mid-Atlantic, staging posts for long flights over seas or as launch pads for amphibious assaults