TOPSHOTS London Underground Piccadilly Line tube trains are parked at the Northfields Depot in west London on August 6, 2015 during a 24-hour strike of Underground staff. Millions of Londoners were forced to walk, cycle or take packed buses to work as Underground staff staged a second strike in a month over plans to run trains all night at weekends. London Underground staff walked out on August 5 evening and will not return until the morning of August 7, causing a shutdown of all 11 lines on the subway network and severely disrupting the capital. AFP PHOTO / LEON NEAL