The East London line is part of the London Overground, running north to south through the East, Docklands and South areas of London. It was previously a line of the London Underground. Built in 1869 by the East London Railway Company, which reused the Thames Tunnel intended for horse-drawn carriages, the line became part of the London Underground network in 1933. After nearly 75 years as part of that network, it closed on 22 December 2007 for an extensive refurbishment and expansion, reopening as part of the Overground network in April 2010. Phase 2, which links the line to the South London line with a terminus at Clapham Junction, opened on 9 December 2012, creating an orbital railway around inner London.