That's an interesting set up.
This sign is much more attractive than the ones we have over here. I have always wonder]d if they have cameras on them. I still make sure to check my speedometer when I see one.
We also have these speed signs around schools. They do slow traffic, even if there is no speed cameras.
It certainly reminds you in a nice way not to speed!
I think that's actually a 20 zone practically all the way from the Duke of Sussex.
Having checked with Streetview it seems you are right and I've edited the description accordingly.
It's quite bonkers. I can understand wanting a 20 zone during school hours, and close to the school, but it's 20mph at all hours of the day. In my experience not all that many people stick to 20mph in the evenings.