London Transport inherited a number of different incompatible electric multiple units from the Metropolitan Railway. Between 1927 and 1933, multiple unit compartment stock had been built in batches by Metropolitan Carriage and Wagon and by Birmingham Carriage and Wagon, to be used on electric services from Baker Street and the City to Watford and Rickmansworth. These were of three incompatible types, with different electrical equipment and engines. In order to make a uniform fleet, units were fitted with Westinghouse brakes and cars with different engines were regeared to allow these to work in multiple with other cars. In 1938, 9 x 8-coach and 10 x 6-coach MW units were redesignated London Underground T Stock. The Buckinghamshire Railway Centre is home to two T Stock carriages.
