It's ok - that sign confused me too and I've lived here all my life. We're a bit behind the times in Wales so I think it's probably the local home guard - did it to confuse the German paratroopers - you know the ones, drop out of the sky dresed as nuns etc..
This pick is quite dark as the sun had only just come up but the little sign actually says no parking.
What a great solution to congestion - flood all the car parks.
I can’t vouch for the validity of this, but I was once told about a sign in the middle of a village pond which just said, “please do not throw stones at this sign”