The Star class, introduced in 1906, was the first in a row of four-cylinder 4-6-0 express locomotives of the Great Western Railway. It actually originated in a 4-4-2 when Churchward built the prototype No. 40 “North Star” in 1906. Based on the three French 4-4-2 compound locomotives bought for trials in 1904 and 1905, he decided to use a similar four-cylinder layout. This meant that the inside cylinders were placed beneath the smokebox and drove the first set of drivers, while the outside cylinders were placed next to the rear axle of the bogie and drove the second set of drivers. But in contrast to the French locomotives, Churchward did not make it a compound and used four cylinders of the same size. The tapered boiler was basically the same as the one used in the Saint class.