High Quality Content by WIKIPEDIA articles! The SR West Country and Battle of Britain classes, collectively known as Light Pacifics or informally as Spam Cans, are classes of air-smoothed 4-6-2 Pacific steam locomotive designed for the Southern Railway by its Chief Mechanical Engineer Oliver Bulleid. Incorporating a number of new developments in British steam locomotive technology, both classes were amongst the first British designs to utilise welding in the construction process, and to use steel fireboxes, which meant that components could be more easily constructed during the wartime austerity and post-war economy.