When O.V.S. Bulleid's 'Merchant Navy' class 4-6-2 appeared on the Southern Railway in 1941, it was controversial. As well as looking unlike any previous steam locomotive, it was full of innovative and untried ideas, and this during the height of the Second World War. A total of 140 such locos were built over the next ten years, 110 of which were a lighter version, the 'West Country'/'Battle of Britain' class. Although all the 'Merchant Navy' locos and many of the 'light' Pacifics were rebuilt by BR to more conventional form, many remained in original form to the end of steam on the Southern Region in 1967. This is the intriguing story of these locos in their original 'air-smoothed' form.