On the R.P.P.R. 'Toffeeapple Farewell' rail tour to Portishead and the Avonmouth dock branch.

I think that the photographer has obtained this fine shot from what I believe is a viewing platform alongside the Portway road linking Bristol and Avonmouth , this scene depicting the Special rounding the " Horseshoe Curve " here between Sea Mills and Shirehampton on the line to Avonmouth and Severn Beach running via Clifton to and from Temple Meads .
The River Avon , visible on the right has the second known and recorded difference in levels between high and low tide of some thirty feet , and it looks low in this view.

This fine overhead view looking towards Sea Mills has this special working heading away from Bristol on the line to Avonmouth and is at Horseshoe Bend with the River Avon at a very low tide on the right .
At this point the line from Sea Mills towards Shirehampton is on a one in sixty four gradient and our cameraman will be on the main A4 Portway road with this narrow bend in the River Avon being the major restriction for vessels navigating the Avon and its massive difference of water levels between high and low tides.