British Thomson-Houston was a British engineering and heavy industrial company, based at Rugby, Warwickshire, England. Originally founded to sell products from the Thomson-Houston Electric Company, it soon became a manufacturer using licences from the American company. BTH merged with the Metropolitan-Vickers company in 1928 to form Associated Electrical Industries, but the two brand identities were maintained until 1960. The holding company, AEI, was bought by GEC in 1967.

On 22 December 1898 BTH opened the Cork Electric Tramways and Lighting Company, followed by the Isle of Thanet Electric Tramways on 4 April 1901 and the Chatham and District Light Railways Company in June 1902. In 1903 BTH was contracted to supply the electrical equipment for the Tyneside Electrics railway network in Newcastle upon Tyne.

In 1931 the Ford Motor Company ordered 3 diesel-electric shunting locomotives for use at their new car plant at Dagenham in Essex. Since they were required to work across the main line to the Company's sidings on the north side, they were built to the LMS loading gauge. These locomotives owed something to an American ‘switcher' design. At the time of building, they were unique in Britain and created considerable interest at home and abroad. 

The locomotives worked for 34 years at Dagenham, during which time each one is estimated to have run well in excess of 250,000 hours. Ford No. 1 was acquired for the K&ESR in 1966 but fitted with the engine from No. 2 which had previously been cannibalised for spares. It saw occasional service on passenger trains during times of high fire risk, but more usually worked permanent way works trains or as yard pilot at Tenterden. It was returned to operating condition in 2000 but is only used on special occasions because of its great age & operational limitation.