I've always wondered what this wheel is for. It's part of the Gridiron's cleaning system. Water is drawn from North Entrance Lock through a sluice channel and could be diverted one way and another across the surface of the gridiron. I wasn't clear from my conversation with the lockkeeper whether this would open the sluice channel or was the control used to divert the water first to the left of this central point of the gridiron, then to the right, but it's definitely part of the cleaning mechanism.
He said he also used to have to go down the ladder and hose it all down after sluicing it out, and that he found the whole process quite fun!
GPS Coordinates:
51.44890, -2.62383
Location: Hotwells
