When Oliver Bulleid was appointed to succeed R. E. L. Maunsell as Chief Mechanical Engineer of the Southern Railway in 1937, most people thought that it was somewhat of a dead end. The Southern Board were committed to extending electrification and the CME's job was considered to be mainly a holding operation until steam traction could be replaced by electric. Things did not work out quite that way however, and the Southern Railway ended up with three of the most advanced steam locomotive designs that ever ran on British metals.

Bulleid, who had previously been the Principal Assistant of Sir Nigel Gresley on the LNER, produced his first designs in the middle of the Second World War and they immediately impressed by their sheer originality and the unusual nature of everything about them. The Class Q1 0-6-0 was uncompromisingly different with no running plates, Boxpok wheels, cubist boiler cladding and outside admission piston valves. They were the most powerful locomotives of their type in Great Britain. When the first of the "Merchant Navy" 4-6-2 "Pacifics" was turned out in 1941, new standards of performance were set over the extremely difficult road between Salisbury and Exeter. However, their sphere of influence was limited due to the axle loading and, at the end of the war, a lighter version was also produced for general use on the Southern. In fact the "West Country" Pacifics were intended for duties similar to the GW Halls, the LMS Black 5s and the LNER B1s but had a greater reserve of power.

In the Locomotive Exchanges of 1948 the West Countries did brilliant work, particularly over the Highland Line from Perth to Inverness. Their high tractive effort, due in part to their 280 psi boiler pressure, gave them a considerable advantage over the types from the other pre-Nationalisation companies once they were on the move. Their starting abilities were not so good due to the low adhesion factor and the weight transfer problem, inherent in all locomotives with a trailing truck underneath the firebox. When in good condition, their work was frequently up to the same standard as the larger Merchant Navies. However one innovative feature introduced by Bulleid, the chain driven valve gear, caused considerable operating and maintenance problems and these came to a head after the locomotives had been transferred over to British Railways on Nationalisation. The chains ran through oil baths and a constant loss of oil and contamination by dirt and grime associated with steam locomotives led the Southern Region of British Railways to rebuild them as conventional locomotives with three independent sets of Walschaerts valve gear. During the rebuilding the air smoothed casing was removed and other items altered to ease maintenance. The rebuilding programme was not rapid, locomotives being attended to as they came up for major overhaul.

"Boscastle" was turned out of Brighton Works in October, 1946 as number 21C139. After running in, it was allocated to Stewarts Lane shed at Battersea and remained there until 1950. It was the regular locomotive for the "Golden Arrow" Pullman Express from London to Dover in 1948 before it was officially named in July of that year. "Boscastle" was one of three members of the class to be loaned to the Great Eastern section in May, 1951 and was officially transferred to Stratford in August, 1951. It returned to Brighton in February, 1952 and spent the next seven years working from there, mainly on the through workings to Salisbury and Bournemouth. During 1959 it was rebuilt at Eastleigh works, and transferred to Bournemouth which remained its home shed until its final transfer to Eastleigh in September, 1962. It remained there until withdrawal in May, 1965 and was moved to Woodham's scrapyard in the following October.

As well as working all over the Southern, from Plymouth to Dover, 34039 also worked on the Somerset and Dorset from Bath to Bournemouth and during its time, on the Great Eastern worked as far north as King's Lynn. But its most unusual appearance must have been when it worked a football excursion from Southampton to Birmingham Snow Hill via Stourbridge junction.

34039 was the first main line steam locomotive to arrive at Loughborough after the formation of the preservation society setting down on GCR metals on 19th January 1973. After a great deal of meticulous restoration, it worked light engine to Rothley as a test run on November 17th 1992 and completed two round trial workings with six coaches on November 19th 1992. It entered traffic on November 21st 1992 and was officially relaunched by Head of the National Railway Museum, Andrew Dow on January 21st 1993. In September 1996, the engine was withdrawn with a bulging firebox. Many firebox stays were replaced over the next fifteen months, the engine returning to traffic for Christmas 1997.

This locomotive is currently out of traffic, awaiting substantial repair work.