The Welsh police are the worst of the lot for these sneaky underhand tactics.
There was a case a while ago where a camera was illegally sited on the M4 during some roadworks. Something like 2500 people were prosecuted. When it was found out the prosecutions were illegal the local authority refused to write to the motorists and let them know - they said they would only remove the points and refund the fines if people came forward - they are quick enough to write in the first place.
Ahh found it
2003 October — South Wales — M4 Newport
2,500 Drivers. £150,000 in fines.
In a tale of staggering ineptitude or deliberate malpractice, a speed camera van targetted part of the M4 outside of a temporary 50mph speed limit due to roadworks. Thousands of drivers on the M4 at Coldra near Newport were wrongly fined.
Despite admitting their 'mistake', the arrogant prats refused to allow a blanket amnesty and insisted drivers would have to apply individually to have their points returned and fines refunded.