RTL vehicles had bodies manufactured by Park Royal, Weymann (30 vehicles) or Metro-Cammell.  The Metro-Cammell bodied buses were RTL 551-1000 (450 vehicles). They had 56 seats, 26 lower, 30 upper.  The RTLs were originally allocated to particular garages which were Leyland-only, resulting in most bus routes being either AEC or Leyland.  In later years some garages had a mixture of AEC and Leyland buses.  As passenger numbers fell during the 1960s, London Transport sold off the Leyland buses, preferring to standardise on AEC vehicles, although some of the Routemasters which eventually replaced the RT were Leyland engined.

RTL 139 entered service at Riverside (Hammersmith) garage in 1949 on routes 17 and 72.  She was withdrawn from service in 1967 and went to a bus museum in Holland.  That museum closed in 1996 and the vehicle was purchased for the London Bus Museum, arriving there in 1998.  She was used in London on various last crew bus days during 2004.  She moved to the new LBM at Brooklands in 2011 and is sometimes used for the Weybridge station shuttle.