This is a detail of King Richard I the pride of the GWR system and as a child my very favourite class of loco. 6000 class 4-6-0 6024. The shed plate 81A shows it lived at Old Oak Common shed which was the main GWR shed at Paddington, the London terminus. This stunning restoration is at the shed at the Didcot Railway Centre.
I spent my youth living first at High Wycombe, on the Paddington - Wolverhampton line, then at Burnham on the Paddington west coast main line. Kings were used on virtually all long distance express passenger trains on those two lines.
(Am I getting overly nostalgic??!!)