I was very interested to read the article on Sunbury and Shepperton Locks, by Nick Pollard, in the October Sunbury Matters, as I joined the Thames Conservancy in 1973, and worked at Riverside Works, Sunbury, for 33 years.
Not knowing exactly what it was, I found the plaque from the old Sunbury Lock Cottage, hidden away behind a shed. This was probably in the early 1990s. I helped to get it returned to the lock.
If the footbridge dates from 1812, the abutment ramps may well date from then, but the bridge deck spanning the river must be a replacement. It is of engineering interest as an early example of pre-stressed concrete (actually it is pre-stressed post tensioned).
Specifically it is made of eleven 6ft pre-cast concrete sections (the length of a cricket pitch?). Steel wires or rods, passed through ducts in the concrete, are tensioned and anchored at both ends, to provide a compression load to keep the sections together, and to carry the loads passing over the bridge.
It may have been an experimental use of the system, which, according to the internet, was developed in the 1930s. I wonder whether the Local History Society can suggest when the work was done?
A further point of interest is that, if I remember correctly, the 1812 Sunbury Lock House is a “twin” of Penton Hook Lock House. Also, thinking about it, could the semi-basement be stables, for when barges were horse-drawn?
At Shepperton the present Lock Keeper’s house was the Thames Conservancy’s Engineer’s office, before the move to Riverside Works Sunbury. There had been a Lock house at the upstream end of the lock, but, I heard, it was bombed during the war. The building on the Lock Island currently occupied by Weybridge Mariners had been the TC workshop.