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.

As with the early members of the Saint class, it was decided to build all further locomotives as 4-6-0 for better adhesion. Even the prototype was rebuilt. In the following years, several small batches were built which were given names of different categories. The complete class became known as Star class after the prototype, the same name as a class of 2-2-2 broad gauge locomotives introduced in 1837. While the first ten built in 1907 received names of stars like the prototype, the second batch of ten from 1908 was named after knights. The third batch of ten from 1909 was named after kings, but became the Monarch class in 1927 when the King class was introduced.

A few of the locomotives of the first batches were built with Swindon No. 1 or No.3 superheaters. Starting in 1909, all others received the No. 3. The ten locomotives named after queens which were built in 1910 and 1911 received the No. 3 superheater from the start. In 1913, five locomotives followed which were named after princes and in 1914, 15 were built which were named after princesses. The last batch of 1922 and 1923 incorporated twelve and was named after Abbeys.

They were able to haul trains of up to 500 tons and could reach up to 90 mph or 145 km/h it the train was not that heavy. Compared to the Saint, their downside was the more complicated maintenance of the inside cylinders and the four valve gears. Nevertheless, Collett designed the Castle and King classes on the same layout due to the good performances of the Star class. 15 members of the star class were even rebuilt to Castles between 1925 and 1940. Most Star class locomotives were withdrawn between 1946 and 1953 and the last four followed until 1957. Only 4003 “Lode Star” was preserved and today is on static display in the National Railway Museum, York.