What was later to become GWR 813 was completed by Hudswell Clarke (works number 555) in June 1901 at a cost of £2,189. As number 26 it was set to work from that Company’s engine shed at Duffryn Yard, Port Talbot.

Following the Railway Act of 1921, the Port Talbot Railway was fully absorbed into the GWR on 1st January 1922 and all the locomotives were allocated numbers in the GWR series proper. Number 26 became GWR number 813 

From the late 1920s the GWR embarked on a programme of replacing much of its ageing fleet of shunting engines together with the many of the non-standard types inherited from companies absorbed and, introduced the ubiquitous 5700 class pannier tank in 1929. Early victims included the Port Talbot Railway saddle tanks and, by 1934 all had been withdrawn from service. Five were sold for further service with the coal industry – three to pits in South Wales and two (including 813) via Robert Stephenson & Co to collieries in the Northeast of England. 

After a few modifications, which included the fitting of Ross Pop valves in place of the GWR safety valves and brass bonnet, Stephenson sold the locomotive to Backworth Collieries Ltd near Newcastle-on-Tyne. There it was re-numbered 12 and put to work on the Backworth system. In 1947 the locomotive passed to newly formed National Coal Board, becoming NCB 11 in 1950.

By 1966, with the contraction of the coal industry and the availability of more modern locomotives, NCB 11 was relegated to the status of spare engine at Backworth and in the following year was offered for sale to the newly formed GWR 813 Preservation Society for the sum of £320