4277 was built at Swindon in 1920 and retained the inside steam pipes to the cylinders.
BR motive power depot allocations since 1948.
| Date Arrived | Depot |
| January 1948 | Duffryn Yard |
| June 1948 | Severn Tunnel Junction |
| July 1953 | Ebbw Junction |
| April 1955 | Aberbeeg |
| July 1963 | Severn Tunnel Junction |
| April 1964 | Aberbeeg |
It was withdrawn in 1964 from Aberbeeg shed and sent for scrap at Barry where it remained until 1986.
4277 was built at the GWR’s Swindon Works in 1920, Works No. 2857. It was painted in unlined green livery with “Great Western” on the tank sides. From 1934 a round GWR logo replaced the lettering, and this in turn was replaced in 1942 by the letters “G W R”.
In 1948 the locomotive passed into British Railways ownership where it was painted in unlined black livery.
In 2008 it was sold to the Dartmouth Steam Railway where it carries the name Hercules. The boiler certificate expired in February 2018. It was taken out of service after running at the Churnet Valley gala in early February 2018.
In February 2021 it was reported that work on the boiler at Riley & son (E) was nearing completion. It was planned that the rolling chassis, complete with a new smokebox made in house, would be transported to Heywood for a trial fitting of the boiler later that month. The frames would then be returned to the Dartmouth Steam Railway to await the completed boiler.
The locomotive was returned to steam in July 2022.
| Home Base | Current Status | Owner |
| Darmouth Steam Railway | Operational | Dartmouth Steam Railway |
Preserved British Steam Locomotives 