Over 2,000,000 speeding tickets were issued in 2017 in the UK ( Scott, The Telegraph, Oct 2018). I don't want one of them so my car has a head-up display and 'detects' speed limits. I also use a Tom-Tom app, Waze and the car's limiter to ensure I don't exceed the limits.
On one road in Lincoln I kept getting warnings on the the Apps and the HUD that I was speeding at 30 mph. On the road there are no repeaters I could see and no 'road furniture' which I understood was required in 20 mph Zones. Currently the penalty for 31 mph in a 20 zone is 4-6 points + 100% of relevant weekly income. The image shows the road where I got the warnings.
So I checked and on the image shown (Google Street view of a school entrance just of Yarborough Rd in Lincoln - hopefully compliant with the Lemon Fool image 'rules') is an entrance to a 20 mph zone (can you see it?). To be fair there is a roundel on the other side of the road and an a attempt at road markings ( i would guess this picture is a couple of years old) but turning into the junction from either direction one's attention is on the School entrance and the pavement. The zone extends much further than the school entrance and well into the housing area further away into the image.
I mentioned this to a couple of police officers and their response was if you get caught take it up with the magistrate - pragmatic of course. My pragmatic response is to do as I mentioned above and 'instrument up' the car to ensure I can stay within the speed limit with my eyes on the road!