(All photos © Philip Lindhurst)
Marooning the Great Northern's former station at Highgate are two pairs of single bore tunnels - Highgate East (139 yards) and the longer Highgate West (332 yards). All four structures are brick-lined with portals fashioned from engineering brick.
The tunnels saw their first traffic in 1867 but remained in public service for less than 100 years - their redundancy notices being activated by British Railways on 4th May 1964. However their ownership was tranferred to London Transport to enable the movement of tube stock between Highgate Wood Sidings - just north of the tunnels - and the Northern Line at Drayton Park. This role ended on 5th October 1970.
The west tunnel's Down bore suffered bomb damage in the Second World War, resulting in its western portal having to be rebuilt in concrete.
The tunnels are now a bat sanctuary, part of an ecological project set up by the Corporation of London and London Underground. Species in residence include Long-eared, Natterers and Daubenton.