In preparation for war, Rolls-Royce and the British Government searched for a location for a shadow factory to ensure production of aero-engines. Crewe, with its excellent road and rail links, as well as being located in the northwest away from the aerial bombing starting in mainland Europe, was a logical choice. Crewe also had extensive open farming land. Construction of the factory started on a 60-acre area on the potato fields of Merrill's Farm in July 1938, with the first Rolls-Royce Merlin aero-engine rolling off the production line five months later. 25,000 Merlin engines were produced and at its peak, in 1943 during World War II, the factory employed 10,000 people. With the war in Europe over and the general move towards the then new jet engines, Rolls-Royce concentrated its aero engine operations at Derby and moved motor car operations to Crewe.