The London Midland and Scottish Railway Class 5 4-6-0, almost universally known as the Black Five, was introduced by William Stanier in 1934 and 842 were built between then and 1951. Members of the class survived to the last day of steam on British Railways in 1968 and eighteen are preserved. This class of locomotive was often a favourite amongst drivers and railway fans.
The last two of the 842 LMS Stanier Black Fives, numbers 44686 and 44687 were constructed by British Railways at Horwich Works in 1951. They were fitted with Caprotti valve gear, raised running plates without splashers, a double chimney and roller bearings on all axles. 44686 and 44687 were fitted with a modified form of valve gear, with an external shaft on each side, driven by a worm gear mounted on a flycrank attached to the middle driving axle.