An empty escalator at Waterloo Underground station, London, as a strike by Underground workers closed the capital's entire Tube system. PRESS ASSOCIATION Photo. Picture date: Wednesday August 5, 2015. Members of four unions are taking industrial action for the second time in a month because of a deadlocked dispute over plans to launch a new all-night service next month. See PA story INDUSTRY Tube. Photo credit should read: Anthony Devlin/PA Wire