The London Midland and Scottish Railway (LMS) Coronation Class is a class of express passenger steam locomotives designed by William Stanier. They were an enlarged and improved version of his previous design, the LMS Princess Royal Class, and on test were the most powerful steam locomotives ever used in Britain at 2,511 dbhp. British Railways locomotive No. 46258 "Robert Stephenson" was built in 1948, and it's the only LMS Coronation Class Locomotive built with 4 sets of Valve Gear, while the other LMS Coronation Class locomotives were built with only 2 sets of Valve Gear. It's also the only 4-cylinder locomotive built with 4 sets of Stephenson Valve Gear.