Peter Kerslake adds "Pioneer Hall class 4-6-0 No 2925 Saint Martin before renumbering as 4900 at Old Oak Common shed in July 1926. The rebuilding took place at Swindon in 1924. Originally built in 1907 Saint Martin was rebuilt in 1924 into what became the forerunner of the Hall class, incorporating smaller driving wheels, a new cab with side windows, no outside steam pipes and a lower pitched boiler. Saint Martin ran in this form until December 1928 when it became 4900, having undergone a three year period of intensive evaluation before the first true "Hall", 4901, emerged from Swindon in 1928."
Photo: F.H. Stingemore/Rail Archive Stephenson