The Scammell Scarab was the successor to the Scammell Mechanical Horse and production began in 1948. In the late 1920s the railway companies were looking for a suitable vehicle to use on their town parcels delivery traffic, which was predominately horse drawn. The London Midland & Scottish Railway experimented with various ideas and in late 1930 announced, jointly with Karrier Motors, a tractor unit for this purpose. The vehicle, the Karrier Cob, was powered by a twin cylinder Jowett engine and utilized a mechanism to couple existing horse trailers to the tractor unit. Meanwhile the London and North Eastern Railway had approached Napier's, the quality car and aero-engine makers for an answer to the same problem. They came up with some ideas, but did not wish to develop the concept and sold