LNER Peppercorn K1 Class

The LNER Peppercorn K1 Class was a series of seventy 2-6-0 Mogul mixed-traffic locomotives designed by Arthur Peppercorn, the LNER's last Chief Mechanical Engineer (1946–1948), based closely on a single prototype rebuilt from Thompson's K4 design by Peppercorn's predecessor, but with important modifications that reflected Peppercorn's own engineering preferences. The K1 was built by the North British Locomotive Company in Glasgow in 1949–1950, entering service under the newly nationalised British Railways rather than the LNER that had ordered them.

The K1 was a capable and well-regarded two-cylinder 2-6-0 suited to the mixed-traffic duties of the former-LNER routes in Scotland and the North East, where the moderate axle loading and Mogul wheel arrangement gave access to routes restricted to heavier types while still providing adequate power for semi-fast passenger and express freight duties. Peppercorn's modifications from the prototype included revised valve events and a simpler two-cylinder layout that gave better reliability in service than the three-cylinder K4s from which the class was derived.

The K1s worked a wide range of duties on former-LNER routes in Scotland and North East England under BR, from the West Highland Line to the Waverley Route, from Tyne goods to North Yorkshire freight. One example, 62005, was preserved and works on the North Yorkshire Moors Railway.