I am sure it is ANPR not speed. They are looking for un-insured/untaxed. The use of the camera sign is just a visable deterant to the public. They use the camera sign on the side of the city warden camera vans round here, too. The two cameras are pointed to read number plates in the different lanes. We see the ANPR vans out a lot when there are political conferences on or royal visits.
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Speed limit sign radio interview. TV
Snap Unhappy“It has never been the rule in this country – I hope it never will be - that suspected criminal offences must automatically be the subject of prosecution” He added that there should be a prosecution: “wherever it appears that the offence or the circumstances of its commission is or are of such a character that a prosecution in respect thereof is required in the public interest”
This approach has been endorsed by Attorney General ever since 1951. CPS Code