From the Wikipedia page 
London Regional Transport (LRT) was the organisation responsible for the public transport network in Greater London, UK from 1984-2000. In common with all London transport authorities from 1933 to 2000, the public name and operational brand of the organisation was London Transport.
The organisation was created by the London Regional Transport Act 1984 and was under direct state control, reporting to the Secretary of State for Transport. It took over responsibility from the Greater London Council in 1984, two years before the GLC was formally abolished.
In 1985 London Underground Limited (LUL) was set up to manage the tube network as a wholly owned subsidiary of London Regional Transport. In 1985 the operation of some bus services was put out to tender for the first time and, for a number of years, buses bearing a variety of different colour-schemes operated alongside those still operating in the traditional red livery. The variety of liveries was found to be confusing to tourists and non-Londoners expecting to find red-painted buses and, after lobbying from the tourist board, it became a requirement when contracts were retendered that bus liveries must be predominately red. Upon privatisation of the main line railways, the Waterloo & City Line passed to the London Underground and LRT management in 1994.
LRT was responsible for some modifications to the fare system, including inclusion of the separately managed British Rail services. In January 1985 the Capitalcard season ticket was launched, offering validity on British Rail as well as London Underground and London Buses. It was priced around 10-15% higher than the Travelcard. In June 1986 the One Day Capitalcard was launched. The Capitalcard brand ended in January 1989 when the Travelcard gained validity on British Rail. In January 1991 Zone 5 was split to create a new Zone 6. The Docklands Light Railway was opened on 31 August 1987 and was included in the zonal Travelcard ticketing scheme.
LRT remained in control of public transport in London until 2000 when Transport for London, an agency of the newly-created Greater London Authority took over responsibility under the Greater London Authority Act 1999.