I think that the answer lies in Roy’s erstwhile Industrial Narrow Gauge Handbook where there is an article on constructing a Birmingham Waterworks pipeline and also, inter alia, on Wheatley’s Springfield Tileries at Stoke-on-Trent. It is the latter article that has a picture of a Ruston emerging from a tunnel with 3 skips on tow. The Tileries lasted relatively late and became popular for visits towards the end so their are quite a lot of photographs in circulation so you might have seen one elsewhere. I haven’t tried but it might be worth Googling the Tileries and seeing what “images” emerge on the internet.
David Woodcock
Champlon, Belgique