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We have already seen one of the ' King Arthur ' engines which up to the war were the mainstay of Southern Railway passenger power. Like the neighbouring Great Western, the S.R. relied on 4-6-0 designs and had never used the Pacific type until in 1941 Mr. p. V. Bulleid, who succeeded Maunsell in 1937, produced the first of his famous ' Merchant Navy ' class.
Although designed in the austerity days of the war, No. 21C1, as the prototype was numbered, embodied many features hitherto little-known in this country. Thermic syphons in the welded steel firebox, 280-lb. boiler pressure and totally enclosed chain-driven valve gear were all revolutionary features to introduce on one locomotive, and even the external appearance was strikingly different, an air-smoothed casing covering the entire boiler and extending back into a streamlined cab and tender. Despite these novel features, No. 21C1 proved highly successful and a further twenty-nine locomotives were constructed, all named after well-known shipping lines. In addition a further 110 locomotives of very similar design but somewhat lighter, known as the ' West Country ' and ' Battle of Britain ' classes, were built and by 1950 the majority of Southern Region passenger trains were worked by these capable machines. Despite their excellent performance, however, the ' Merchant Navy ' engines particularly were heavy on coal and oil, and in 1956 a start was made on rebuilding them with conventional Walschaerts valve gear. At the same time the streamlined casing was removed, as shown in our picture of ' Cunard White Star.' Many have been withdrawn, and with the electrification of the line to Bournemouth by 1967, it is expected that the last of the class will go. They will, nevertheless, be the last main line steam passenger engines to work regular express runs.
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