The London and North Eastern RailwayClass V4 was a class of 2-6-2steam locomotive designed by Sir Nigel Gresley for mixed-traffic use. It was Gresley's last design for the LNER before he died in 1941. The V4s had similarities in their appearance and mechanical layout to the V2 "Green Arrow" class. The V2s, introduced some years previously, were large and heavy locomotives, with very limited route availability. The V4 was a lightweight alternative, suitable for use over the whole of the LNER network.
Two locomotives were built at the LNER's Doncaster Works in 1941. The first engine, 3401 Bantam Cock, had a scaled-down version of the Gresley Pacific boiler with a grate area of 27.5 sq ft. Its tractive effort of 27,000 lbs was produced by boiler pressure of 250 psi and three cylinders of 15-inch diameter. The second locomotive, 3402, incorporated a fully welded steel firebox and a single thermic syphon for water circulation. It was not named, but was known unofficially as "Bantam Hen".
The type was tried on the Great Eastern section of the LNER, and was well received, with more power than the existing B17's and better riding qualities. It was anticipated that many more would be produced, but after the death of Gresley and his succession by Edward Thompson, no more were built. Instead, the LNER Thompson Class B1 was adopted as the LNER's standard mixed-traffic locomotive.
The two locomotives were sent to Scotland for use on the West Highland Line, although their wheel arrangement was not particularly suitable for the steep gradients on the line. They were renumbered 1700 and 1701 in 1946, and later became British Railways 61700 and 61701.