LNER N7 Class

The LNER N7 Class was a series of 134 outside-cylinder 0-6-2 side-tank locomotives designed by Alfred Hill for the Great Eastern Railway and completed under Nigel Gresley for the LNER from 1925, built specifically for the intensive suburban passenger services on the Great Eastern's steam-operated London suburban network radiating from Liverpool Street station. The N7 became the standard GE suburban tank engine of the 1920s–1950s, working the intensive Liverpool Street–Enfield Town, Liverpool Street–Chingford, and other GE suburban services until electrification progressively replaced steam from 1960.

The 0-6-2T wheel arrangement gave six coupled driving wheels for strong acceleration from the frequent suburban stops and the trailing bogie for stability at moderate running speeds, while the side tanks and bunker provided adequate fuel and water for the intensive turn-round times of GE suburban working. The N7 was built with outside Walschaerts valve gear and outside cylinders for accessibility, and Gresley introduced minor detail improvements as the LNER built further batches through the 1920s.

The N7s were the locomotives that worked Liverpool Street's suburban services for thirty years, a traffic among the most intensive in Britain at its peak. Their replacement came not from steam but from BR Class 306 electric multiple units when the former-GE suburban lines were electrified on the 25 kV AC overhead system from 1960. One example, 69621, is preserved at the Epping Ongar Railway in Essex, operating on a section of the former GE suburban line.