I think the corridor you can see running from the back of the building on Sion Hill to the building on the right, on Sion Lane, is part of the old Saint Vincent Rocks Hotel. It was converted into houses, and the front bit, just the main building on Sion Hill, called Trafalgar House now, was on the market for £1,550,000 back in 2019.
The listing mentions:
To the rear a late C19 long brick extension raised on open arches
...anyway. I think it's likely the Sion Lane building was a hotel annex, though I think it's separate flats now. I wonder which of the two sides owns the corridor between them, assuming it really is a corridor? Or maybe even that's flats now...
Next time maybe I'll wander across the green bit and see what I can see over the wall. I think the area just used to be the hotel car park, but there might be more interesting things to see.
GPS Coordinates:
51.45401, -2.62436
Location: Clifton Village