Thameslink is a 24-hour, 115-station (32 managed) main-line route in the British railway system, running from Bedford, Luton, St Albans City, Peterborough and Cambridge via central London to Sutton, Orpington, Sevenoaks, Rainham, Horsham and Brighton. The network opened as a through service in 1988, with severe overcrowding by 1998, carrying more than 28,000 passengers in the morning peak. All the services are currently operated by Govia Thameslink Railway.

The Thameslink Programme is a major £5.5 billion scheme to increase capacity on the central London section by accommodating more frequent and longer trains. The upgrade was scheduled for completion in 2019. In 2016, new Class 700 trains started operating on the route and replaced the Class 319, Class 377 and Class 387 trains which were withdrawn and transferred elsewhere. There is a lot of debate as to whether this line 'belongs" on the Tube Map, or not, as it is not really an Underground service, but does connect with the underground. Although Thameslink has been showing on London Connections maps over the years, it appeared on the Tube Map in December 2020, this was to assist with social distancing when Coronavirus struck the UK and it was needed to show people that there alternative connections available. 

Depots.