A 97-year-old Southern Railway (SR) 2-6-0 light passenger steam locomotive is to join the roster of visiting engines for the Gloucestershire Warwickshire Steam Railway's (GWSR) Cotswold Festival of Steam from May 12-14.

The locomotive in question is SR 'U' Class 2-6-0 Mogul No. 31806, and is appearing courtesy of the Swanage Railway and JMB Locomotive Services.

Time for a little bit of history on the Southern's link with Cheltenham and 'U' Class No. 31806.

The SR reached Cheltenham via the former Midland & South Western Junction Railway from Andover via Swindon, Cirencester and Andoversford. At Cheltenham, the SR trains originally used the former Midland station at Cheltenham Spa but latterly Cheltenham St. James, the SR locomotives being serviced at Cheltenham Malvern Road depot. 31806, which is known to have visited Cheltenham, is one of Richard Maunsell's attractive and successful light passenger engines introduced in 1928.

The design took many principles from Churchward's GW locomotives including long-travel valves. The first 20, including 31806, were rebuilds of Maunsell's ill-fated 'River' ('K') Class 2-6-4Ts, with the 'U' Class's development and construction being accelerated in part as a result of the Sevenoaks railway accident on 24th August 1927. The 50 members of the class were built (or re-built) at Ashford, Brighton and Eastleigh.

31806 was re-built at Brighton in 1928 from a 1926 2-6-4T - 'K' Class No. A806 'River Torridge'. The class gained the nickname 'U-Boats' after the submarine warfare of the First World War.

Locomotive A806 entered service in 1928 and by nationalisation it had spent time at Nine Elms (9E, circa 21st March 1932) Basingstoke (BAS, 1939), Redhill (RED), and Guildford (GFD) sheds. The 'U' Class numbering was rationalised when the final batch of 'U's were constructed between 1932 & 1934, which resulted in the 'A' prefix being dropped and replaced with a '1'.

Records indicate that A806 left Ashford Works paint shop on the 1st September 1932, wearing the number 1806. By December 1934, the locomotive had acquired the rather distinctive 'half height' smoke deflectors.

In 1945, 1806 underwent minor repairs at Guildford (GFD) and the loco remained there until after nationalisation. It left the paint shop on the 1st April 1949 renumbered as 31806 and wearing BR Mixed Traffic Black livery. 

As the 1960s was approaching, it was evident that a number of the class were suffering from cracks in the light weight frames and worn out cylinders. In September 1957, having covered nearly 836,000 miles, 31806 travelled to Ashford Works where it was fitted with a 'new front end' which comprised of a new blast pipe, chimney and BR type 4 cylinder blocks. In addition, its tender was swapped back to the same 3500-gallon type which it had been supplied with in 1928.

The locomotive retuned to traffic on the 1st November 1957. Records indicate that the last modification made during its SR/BR career was the fitment of the Automatic Waning System (AWS). This work was carried out at some point between 1957 and April 1963 when it returned to Guildford (70C).

Its successful career ended when it was withdrawn at Guildford shed on the 5th January 1964 after 34 years & 7 months of service, by which time it had covered nearly 1 million miles. Later in 1964, it was sent to Woodham's Scrapyard at Barry, South Wales where it remained for over 12 years.

The locomotive was rescued by John Bunch for preservation at the Mid-Hants Railway in October 1976. Restoration commenced in 1979 and 31806 was returned to service in April 1981.

After 10 years of service at the Mid-Hants Railway, its boiler ticket expired and the locomotive remained out of service pending overhaul. 31806 eventually re-entered traffic on the railway in 2011. In 2014, it moved to its current home at the Swanage Railway and forms part of the railway's resident fleet. The 'U-Boat' has proven to be easy to maintain, efficient and is very popular with the locomotive crews and visitors alike.

The engine is the oldest of the four 'U' Classes in preservation and the only 'River' rebuild still in existence.

Tickets for the Festival are available online via the GWSR website. With up to eight steam locomotives running, it will offer an action-packed timetable of trains, including goods trains and shunting demonstrations.

The locomotive and carriage & wagon workshops will throw open their doors for rare behind-the-scenes visits and there will be plenty of other activity at the railway's stations. The opportunity to travel between the only operational 'U' is not to be missed.

The 'U-Boat' is the fifth visiting engine to be confirmed. Four other visiting locomotives have been confirmed for the event: Standard Class 4 4-6-0 No. 75014 Braveheart, appearing courtesy of the Dartmouth Steam Railway, Great Western Railway 'Castle' Class No. 4079 Pendennis Castle, appearing courtesy of the Great Western Society at Didcot Railway Centre, L&Y 'Pug' No. 11243, appearing courtesy of the Lancashire & Yorkshire Trust based on the East Lancashire Railway, and Standard Class 2 2-6-0 No. 78019, appearing courtesy of the Loughborough Standard Locomotive Group and the Great Central Railway.