These were medium-sized Prairie tank engines used for suburban and local passenger services throughout the Great Western Railway. The class was an updated version by C B Collett (1871-1952) of G J Churchward (1857-1933) Class 3100/5100 of 1903. The original 40 members of the 3100 class had been renumbered 5100 and 5111 to 5149 in 1927. The first batches of 5101s filled in the numbers 5101 to 5110 and extended the class to 5189. They were really little changed from the first batch, having an increased axle loading of 17 tons 12 cwt; the maximum permitted for the ‘Blue’ route availability. Bunkers were of the standard Collett design with greater coal capacity. The 5100 series was exhausted in 1934, and further lots were numbered from 4100. 4160-4179 were built in 1948/9 so technically were never GWR locomotives.

No. 4160 was built at Swindon Works and entered service in September 1948. Withdrawn June 1965 arriving at Barry scrap yard in August 1965. First moved to Birmingham railway Museum in August 1974 then to the Plym Valley railway in May 1981. From there it went to the West Somerset Railway in the 1990s where it was returned to steam by a volunteer group.