Northern City Line

From the Wikipedia page

The Northern City Line is a railway line from Moorgate Station to Finsbury Park Station in London, once part of the Great Northern Electrics line. It should not be confused with the City branch of the Northern line, nor with the North London Line. The line is underground from Moorgate to Drayton Park, and runs in a cutting from there until meeting the East Coast Main Line south of Finsbury Park.

The line was formerly part of London Underground, and during its history has been part of both the Metropolitan and Northern lines, although it is connected to neither. It is now part of the National Rail network and is owned by Network Rail. The line is served by London commuter trains run by First Capital Connect on the lines London Moorgate - Welwyn Garden City and London Moorgate - Hertford North - (Letchworth Garden City).