Peter Kerslake says ""The 61xx 2-6-2Ts introduced in 1931 were a development of the earlier 31xx and 51xx classes. They were principally for use within the London suburban areas on local passenger work with increased boiler pressure producing increased tractive effort from the earlier engines.
The class remained in service until the late 'fifties and those examples working within the lines of the London Transport network were fitted with an automatic braking system together with a modified form of the Automatic Train Control apparatus, adapted for use over the electrified lines.
6150 had been a Slough based engine in earlier years, although the majority of the class were at Reading and at Old Oak Common.
They remained in service until 1965 when the last nine were condemned including 6106 which was preserved following withdrawal from Oxford and which is now based at Didcot, the Great Western Society's depot."