I don't know the circumstances of this trip, but 51 managed to get out of town not long before its final withdrawal from passenger service and is here at Aberdare Urban District Council's depot in Gadlys.
The standard BR 16 Ton mineral wagons in the background show that the coal industry was still very much alive at this time.
Aberdare UDC 39 is from the first and largest batch of (seven) Bristol REs, with the other deliveries being to Cynon Valley. This batch largely displaced the remaining Guy Arabs, including the last double-deckers in the fleet.
From an original slide in the David Beilby collection, photographer unknown
