Under the control of the Greater London Council, London Transport introduced in 1981 a system of fare zones for buses and underground trains that cut the average fare. Fares increased following a legal challenge but the fare zones were retained, and in the mid-1980s the Travelcard and the Capitalcard were introduced. In the early years of the 21st century, London Underground was reorganised in a public–private partnership where private companies upgraded and maintained the infrastructure. In 2003 control passed to Transport for 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.