The LMS 'Coronation' Class were an enlarged and improved version of William Stanier's earlier LMS 'Princess Royal' Class, and on test were the most powerful steam locomotives ever used in Britain at 2,511 dbhp, specifically designed for power. The intention from the start was to use them on express services between London Euston and Glasgow Central; their duties were to include the hauling of a proposed non-stop express, subsequently named the Coronation Scot.

The first ten locomotives of the 'Coronation's were built in a streamlined form in 1937 by the addition of a steel streamlined casing. 6222 was rare for the Class in that it was named after a Queen, specifically The Queen Mary rather than a Princess. While many 'Princess Coronation' locomotives have been preserved, sadly 'Queen Mary' was withdrawn in October 1963, and scrapped in November.