NER Class V/09 [LNER C7]

The NER Class V/09, more widely known as the Z Class and designated LNER C7 after the 1923 Grouping, was a series of 50 three-cylinder simple-expansion 4-4-2 Atlantic express passenger locomotives designed by Vincent Raven and built at Darlington Works between 1911 and 1918, representing the pinnacle of North Eastern Railway express locomotive development and one of the finest Atlantic types in Britain. The Z Class gave the NER outstanding performance on the East Coast Main Line's most demanding express workings, and the three-cylinder arrangement provided exceptionally smooth power delivery that was noticed and appreciated by both crews and passengers on the Anglo-Scottish services.

Raven designed the Z Class as a development of Wilson Worsdell's Class V Atlantic, applying three-cylinder simple expansion — with all three cylinders driving the same coupled axle, avoiding the coupling and balancing problems of Webb's uncoupled designs — and superheating to produce a locomotive of sustained high power for the longest and heaviest ECML workings. The three-cylinder layout gave very smooth torque with six power impulses per revolution of the driving wheels rather than four from a two-cylinder engine, dramatically reducing the hammer-blow on the track and the surging motion that fatigued crews on long runs at high speed.

In service the Z Class Atlantics gave the NER, and subsequently the LNER, outstanding express performance on the York–Newcastle and Newcastle–Edinburgh sections of the ECML. Gresley's Pacifics eventually superseded them on the heaviest East Coast expresses, but the Z Class remained in service on secondary express and semi-fast duties well into the LNER era. A particularly celebrated incident occurred in 1923 when a Z Class Atlantic made an emergency run from Edinburgh to York at an average speed that attracted considerable attention and demonstrated the class's performance capability. None of the Z Class was preserved, which is a significant loss given the class's historical importance as the NER's greatest express type.