London ⁱ/ˈlʌndən/ is the capital city of England and the United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its founding by the Romans, who named it Londinium. London's ancient core, the City of London, largely retains its square-mile mediaeval boundaries. Since at least the 19th century, the name London has also referred to the metropolis developed around this core. The bulk of this conurbation forms the London region and the Greater London administrative area, governed by the elected Mayor of London and the London Assembly.

London is a leading global city, with strengths in the arts, commerce, education, entertainment, fashion, finance, healthcare, media, professional services, research and development, tourism and transport all contributing to its prominence. It is the world's leading financial centre alongside New York City and has the fifth-largest city GDP in the world (and the largest in Europe). London has been described as a world cultural capital. It was the world's most visited city during 2011 and London Heathrow is the world's busiest airport by number of international passengers. London's 43 universities form the largest concentration of higher education in Europe. In 2012 London will become the first city to host the modern Summer Olympic Games three times.

Demand Responsive Transport or Demand-Responsive Transit (DRT) or Demand Responsive Service or Dial-a-ride or Flexible Transport Services is "an advanced, user-oriented form of public transport characterised by flexible routing and scheduling of small/medium vehicles operating in shared-ride mode between pick-up and drop-off locations according to passengers needs". In many areas DRT is instead known as DART, or Dial-a-Ride Transit.

DRT systems provide a public transport service in rural areas or areas of low passenger demand, where a regular bus service may not be as viable. As such, DRT schemes for may be fully or partially funded by the local transit authority, as providers of socially necessary transport. As such, operators of DRT schemes may be selected by public tendering. Other schemes may be partially or fully self-funded as community centred not for profit social enterprises (such as a Community interest company in the UK).

DRT schemes may also be provided by private companies for commercial reasons; some conventional bus operating companies have set up DRT-style airport bus services, which compete with larger private hire airport shuttle companies.