One of two U class locomotives on the Bluebell Railway, both coming via Barry scrapyard, this one was privately purchased and donated to the Bluebell, which has loaned it to the Maunsell Locomotive Society on a long-term basis. 1638 lost its tender while at Barry, so a new one has been built, starting from the remains of a snowplough purchased by the late George Nickson which was the tender of schools class "Malvern" originally. The loco steamed for the first time in preservation in February 2006.

The Society won three awards for the restoration of 1638, including the prestigious Heritage Railway Association’s John Coiley Award for Locomotive Projects. The citation reads ‘For restoring and maintaining their fleet of Maunsell Locomotives, as exemplified by the restoration of ‘U’ Class 2-6-0 No.1638 from scrapyard condition’. The loco ran on the Bluebell Railway for ten years and was withdrawn in 2016. It now requires another thorough overhaul, including replacement of its driving wheel tyres which are down to scrapping size.

Built in 1931 at Ashford, 1638 initially worked from Redhill, but was reallocated in 1933 to Guildford, where it worked on the North Downs line to Redhill and Tonbridge. It then had a brief stay at Bournemouth shed following an overhaul in 1936, but was moved to Reading in 1937. 1638 stayed here for six years before being moved to Exmouth Junction in 1943. In 1946 it was surplus to requirements and was put into store at Eastleigh for a year before being returned to Exmouth Junction. In 1949, renumbered 31638, it moved to Stewarts Lane shed. The engine then moved several times, being allocated to Faversham, Hither Green, Redhill, Brighton, Eastleigh and Redhill (again) before finally settling at Fratton in 1953. Here it stayed until the shed closed in 1959, when it moved to its final shed, Guildford. 31618 stayed at Guildford until withdrawal from service in 1964.

The restoration of this U class loco was the biggest challenge tackled by the Maunsell Locomotive Society (working in conjunction with the Bluebell Railway). It lacked many components (including a tender) and was in a very run-down condition. Virtually all the motion parts (coupling rods, connecting rods, etc.) were missing, along with all its brass fittings. One new crank pin was required, and some driving wheel spokes had to be welded up where they had been severed with gas cutting gear. The tyres needed turning and the axleboxes had to be re-metalled and machined. The boiler required both a new tubeplate and major repairs to the firebox steel outer wrapper, in addition to the usual replacement of boiler tubes.