London Underground today apologised to passengers for delays to Tube journeys during this morning's rush hour, partly caused by a discarded newspaper becoming lodged in track equipment.
Services on the Victoria and Piccadilly lines were affected, leading one union official to describe today as "black Friday" for travellers in the capital.
Howard Collins, London Underground's chief operating officer, said: "We apologise to passengers who have faced disrupted journeys to work this morning. The Victoria line was suspended earlier between Brixton and Victoria owing to a signal failure caused by discarded newspaper having become lodged in a crucial part of the track equipment outside Brixton.
"Our engineers attended and worked flat-out to resume the service as quickly as possible. There were also problems earlier on the Piccadilly line with the line suspended for a short time following a track circuit failure at Hammersmith.
"Our staff right across the network are working tirelessly to upgrade the network and improve reliability."
Bob Crow, general secretary of the Rail, Maritime and Transport union, said: "This is yet another Black Friday for Tube users and another example of the maintenance and investment backlog hitting services."