The Great Western Railway King class consisted of 30 4-6-0 express locomotives introduced in 1927.
The class was developed under Chief Mechanical Engineer Charles Collett to handle increasingly heavy express trains on the Great Western main line.
Kings used very large boilers and four-cylinder propulsion while retaining the GWR preference for the 4-6-0 wheel arrangement rather than adopting a Pacific layout.
Their high axle load restricted them to routes and bridges capable of carrying the weight.
The class became associated with major express services from London Paddington to destinations in western England and South Wales.
King George V, the first of the class, traveled to the United States in 1927 for the Baltimore & Ohio Railroad centenary celebrations.
World War II and postwar operation altered liveries, maintenance practice, and train assignments.
British Railways withdrew the class during the early 1960s as diesel traction replaced steam on principal routes.
Three King class locomotives survive in preservation.
For TransitSatellite, the engineering story should emphasize route compatibility: raw locomotive power was useful only where bridges, track, clearances, and axle-loading standards could support it.