Soon after the railways were nationalised in 1948, the then recently formed British Railways Board (BRB) undertook a review of the locomotive stock which had been inherited from the 'Big Four' independent railway companies. It soon became apparent that the whole stable of steam locomotives comprised of a huge variety of different class types, vast numbers of which were getting close to or in some cases, were already life-expired.

Right from the beginning the government-owned organisation needed to reduce costs as soon and as practical as possible. Not an easy task with a war-battered railway. However, work began straight away and in its first year, the BRB had recruited the renowned locomotive engineer Robert A Riddles, formerly of the LMS, to take responsibility for the Mechanical & Electrical Engineering department. Riddles was given the task of developing a new small range of new steam locomotive designs, the intention being that they replace the older pre-nationalisation locomotives.

Riddles' settled for a plan of action which was to use the best pre-nationalisation designs and incorporate the best qualities of each into his standardised locomotives, thus amalgamating the greatest engineering feats from all of the former railway companies. The first step towards creating the new designs were the 'Locomotive Exchange Trials'. Riddles started his quest by selecting a number of express type locomotives from each of the newly-formed Regions and utilising them on ''foreign'' territory. As an example, LMS locomotives operated over the Southern Region where there were no water troughs. To compensate for this they were married together with four-axled ex-War Department tenders with larger water tanks. These were specifically given LMS lettering for the occasion. Similarly, ex-Southern Region types used elsewhere were married together with ex-LMS tenders with water scoops. This yielded some important information for the design team on how suitable particular locomotive classes were to certain stretches of line.

On completion of the Locomotive Exchange Trials, Riddles' Chief Draftsmen went back to the drawing board and began to formulate the first of the then new 'standardised' steam locomotives. Officially, these trials were to identify the best aspects of the four different approaches to locomotive design so that they could be used in the new BR standard designs. However, the methods used for testing lacked any real scientific value, and taking Riddles' background into consideration and other political influences, it was almost predictable that LMS practice was largely followed by the new standard designs regardless, and it is therefore hardly surprising that nearly all of Riddles' final products would bear much resemblance to the designs pioneered by the LMS, particularly those locomotives which were designes of Stanier and Ivatt.

However, the trials were useful publicity for BR to show the unity of the new British Railways. By 1950 the first of the new express locomotive designs had been finalised at Derby and in the same year, the British Transport Commission placed an order with Crewe Works for the construction of twenty-four of the type. What came forth from Crewe on 2nd January 1951 was a 4-6-2 Pacific locomotive looking conspicuously like the Coronation class of engines designed by William Stanier, also formerly of the LMS. The imposing engine, finished in a plain black scheme with no lining, was scheduled for a test run between Crewe and Carlisle on 11th January 1951, a dynamometer carriage being one of the consists of the train it was to haul. Following the test run, which proved to be a promising start for the type, the locomotive, numbered 70000, was repainted into the much more familiar lined BR Brunswick Green and delivered to Marylebone station on the last but one day of January to be named. No. 70000 was appropriately called 'Britannia', after the female personification of the British Empire, and it marked a very promising step forward for BR.

To commemorate the Sixtieth Anniversary of the 1948 Locomotive Exchange Trials, in 2008 Hornby Railways produced a Limited Edition Model of a 4-6-2 West Country Class Locomotive 'Bude' No 34006. This model, represents the classic pairing of a Southern Region Bulleid Pacific with a Stanier Tender. For the collectors out there, the Hornby R2685 West Country Class 'Bude' with Stanier Tender was only produced in a limited run of 2008 and each of the model trains came with a numbered Certificate of Authentication.

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