The Northern line is currently being upgraded as part of London Underground's Investment Programme. Tube Lines, the PPP company responsible for delivering the upgrade work, will begin a programme of closures to the line from the end of March.

Transport for London believe that Tube Lines' demands for access go well beyond what is necessary, and would result in significant disruption to customers using that line.

London Underground's current understanding is that Tube Lines' plan demands 65 weekend closures to part or all of the line, starting at the end of March and running until November 2011 including long weekend closures at Christmas, Easter and other bank holidays. In addition, Tube Lines are planning 16 months of early weekday closures (Monday to Thursday) of the whole line north of Stockwell starting in July 2010, which would mean that the last trains from Central London woudl leave by around 22.30.

In order to prepare for the upcoming closures, Transport for London is providing several ways of obtaining information:

- Online at http://www.tfl.gov.uk/traveltools
- Articles and items in the London media including the Metro newspaper
- Travel information telephone line on 020 7222 1234 (24 hours) or customer services on 0845 330 9880 (8 am to 8 pm, 7 days a week)
- Targeted e-mails sent to customers
- Teletext p. 164 and Ceefax p. 436
- Posters and leaflets at Tube stations, and at National Rail stations in the South-East
- Train and station announcements