Police spotting (junction watch)

Any road sign that is circular with a red outline generally means "no ------" in the UK.

E.g. the "no motor vehicles" / low flying motorcycles one:

Anyone who has studied for a driving test should know that, but of course a significant number of cyclists never have.

http://www.driving-test-success.com/uk-road-signs03.htm

Dumbest signage ever.

What does this mean ^

No 40 year olds? You can do any speed you want except 40mph? See? Fucking stupid signs.

^ Why do they cross these ones out?