Crowd control measures were in place at Finsbury Park this morning as the entire Piccadilly Line was hit by severe delays after a signal failure at Hyde Park Corner.
Transport for London warned passengers at Finsbury Park to use nearby stations and bus services instead of the Tube, and said both the Underground and Great Northern services were "very busy".
It also warned other Piccadilly Line passengers to find other ways to work.
"Trains are likely to be very crowded and journey times are much longer than usual," it said.
Finsbury Pk: Crowd control measures in place to prevent overcrowding. Pls use nearby stations. Tube & Great Northern services are very busy.— Piccadilly line (@piccadillyline) September 4, 2017
The delays came after engineers completing works at Hyde Park corner discovered a faulty signal, a spokesperson for Transport for London (TfL) said. That caused the engineering team to be late handing possession of the track back to the day team.
"TfL apologises to customers for the delays to services this morning and we are working to get a good service running as quickly as possible," he added.