Airports of London cannot be expanded due to the docks on either side. It is also the only airport serving London which does not operate at night. A light rail service from London City Airport DLR station, which adjoins the terminal building of London City Airport, links it to the financial district of the City of London at Bank and Monument stations, which offer interchanges with London Underground. Located in the London Borough of Hillingdon, Heathrow is by far the largest of London's airports and considered the main gateway into the United Kingdom for non-European visitors. Heathrow has four terminals and two parallel
History of the London Underground London (TfL), which had been opposed to the arrangement and, following financial failure of the infrastructure companies, had taken full responsibility by 2010. The contactless Oyster card first went on sale in 2003. The East London line closed in 2007 to be converted into a London Overground line, and in December 2009 the Circle line changed from serving a closed loop around the centre of London to a spiral also serving Hammersmith. Currently there is an upgrade programme to increase capacity on several Underground lines, and work is under way on a Northern line extension to Battersea. In the first