The Peppercorn class A1 was a Pacific that has been designed for the LNER, but was only introduced after the founding of British Railways. It had three cylinders and a double Kylchap blast pipe. In 1948 and 1949, 49 were built at Doncaster and Darlington. Since most Gresley A1 had been rebuilt to A3, the designation A1 was again available. The names of the locomotives were not uniform and had several subjects.

Usually, they hauled heavy express trains of up to 15 coaches at speeds of 60 to 70 mph (97 to 113 km/h). The first ones were already withdrawn in 1962 and by summer 2008, all had been scrapped. Between 1994 and 2008, the A1 Steam Locomotive Trust constructed No. 60163 “Tornado”, which became the 50th A1. In 2017, it became the first steam locomotive to reach 100 mph (161 km/h) in Britain after commercial steam service officially ended in 1968.