I was playing with the picture you have of the quarry and the strange trail of smoke.
Looking at it hard through a very big enlargement you can see:
a) The steam plume is flattened as the equipment is moving, ie a long flat plume dispersing in the wind as seen in many classic steam loco photographs.
b) The photo shows the very top of a chimney and the base of a loco (I think) with a cloud of dust or smoke obscuring most of it.
I thought the plume was too high for a loco on the track until I saw this photo of an SDR loco and saw how high the body an chimney were, at least twice the height of the guy leaning against the frames.
If you do a crude scaling then the height of the plume works for the top of one of the very tall old locos.
Perhaps maybe? John Root
A rail shuttle service to Cranmore was provided from Westbury via Witham. From Cranmore a fleet of vintage buses provided a service to the quarry. A number of steam and diesel locomotives were on display and in action.