31625 was built at Ashford Works in 1929. In 1947 it was converted to oil burning as an experiment but reverted to coal burning the following year.
BR motive power depot allocations since 1948.
| Date Arrived | Depot |
| January 1948 | Exmouth Junction |
| May 1948 | Fratton |
| October 1948 | Nine Elms |
| April 1951 | Guildford |
| July 1953 | Eastleigh |
| September 1953 | Guildford |
I January 1959 the locomotive received completely new frames at its last general overhaul.
It was being withdrawn in January 1964 and sold to Woodham Brothers in Barry for scrap. It arrived in Barry in June 1964 remained at there for nearly16 years – leaving in March 1980.
It was purchased by John Bunch and based on the Mid Hants Railway but in 2014 the owner moved it to the Swanage Railway who agreed a 25 year lease for the locomotive.
Whilst based on the Mid Hants Railway 31625 took part in the Steam on the Met events on the Metropolitan Line of the London underground between Harrow-on-the-Hill and Watford.
31625 last hauled a train in 2001 and is the only U class locomotive with a British Railways modified front end.
It is currently stored off site near Corfe Castle station awaiting an overhaul which is anticipated to commence in 2017 or 2018 but had still not started by January 2020.
| Home Base | Current Status | Owner |
| Swanage Railway | Stored awaiting overhaul | John Bunch |
- 31618 (SR A618, SR 1618 & BR 31618)
- 31638 (SR A638, SR 1638 & BR 31638)
- 31806 (SR A806, SR 1806 & BR 31806)
Preserved British Steam Locomotives 