GN Electrics Line
This line has an involved early history, the full details of which are on CULG: http://www.davros.org/rail/culg/northern.html
When London Transport was formed, the line was part of the tube network, running a shuttle service between Finsbury Park and Moorgate; It was called the Northern City Line; in 1970 it was renamed the Northern Line - Highbury Branch.
February 1975 saw the Moorgate Tube Disaster, in which a train on his line crashed the barriers at Moorgate causing injuries to many passengers. This saw the closing of the line, and its removal from the tube network.
1976 saw the line reopened by British Rail, extending the service to beyond Finsbury Park - linking with their existing services from King's Cross. The line was renamed the GN Electrics line, and operated the services that it does at present.
The present day
Privatization saw the line being run by WAGN.