This is a water wheel at the Saxon Mill (now a pub/restaurant) on the outskirts of Warwick, which as far as I know, doesn't operate anything.

You can see water from the river (quite high at present), raging though. At times when the river is high the wheel is turned off - and isn't allowed to rotate.

This is done for safety in this situation, as when the water gushes through at this rate, if the wheel were to work, it could risk causing a good deal of damage I've been told - to the wheel in particular.

You shouldn't see the water nearly halfway up the wheel.