34067 near Bath in September 2011. ©Hugh Llewelyn
The SR West Country and Battle of Britain classes, collectively known as Light Pacifics or informally as Spam Cans, are air-smoothed 4-6-2 Pacific steam locomotives designed for the Southern Railway by its Chief Mechanical Engineer Oliver Bulleid. Incorporating a number of new developments in British steam locomotive technology, they were amongst the first British designs to use welding in the construction process, and to use steel fireboxes, which meant that components could be more easily constructed under wartime austerity and post-war economy.
(Information provided via Wikipedia)