I found this on an auction site:
Built in Ingatestone, Essex by the Larmar Engineering Co Ltd and first introduced in 1946, the single-seater Larmar Monocar was designed primarily for invalids, for whom the main attraction was its ability to fit through a doorway - the vehicle was only 28½" wide! The Larmar was powered by a BSA 249cc single-cylinder air-cooled motorcycle engine, as fitted to the Birmingham firm's C10 and C11 models, which was mounted behind the driver and drove only one of the two rear wheels. Sliding-pillar front suspension and independent rear suspension made for a relatively comfortable ride, while top speed was a giddy 35mph. More refined than the majority of invalid carriages of the day, the Larmar came with a single headlight, folding convertible hood and a windscreen, and was later made available in improved form with a 350cc engine. Production ceased in 1951.