Speeding

[Joe 90]

spoke to my mum last night and it would seem she's got into a spot of bother.

You see theres this road round here, its been a 40 road for as long as I can remember. Anyway my mum was going down it yesterday and she got flagged down by an officer of the law.
He asked if she knew the speed limit, 40 she replied. To which he informed her that the speed limit had recently been changed, and showed her a reading that she'd been doing 39. Obviously a speeding ticket etc followed.

Now, you see, the same happened at the top of this road recently but that came with huge new bright green 30 signs. This road in question though simply has a red sign saying 'police: speed limit recently changed' or something...

I'm of the understanding that if the limit has recently changed, and its not got any 30 signs on the road, then you can surely not be charged?

Furthermore, we're currently waiting on a mortgage to move into our new house and 95% of our stuff is in a storage locker. My mums driving license is somewhere in that lot. So whats the deal with document declaration, we recently hired a car without a driving license... they just looked it up on the DVLA - will the police do the same with a decent explanation to said situation?