Rear facing roof mounted periscope camera on Police Vectra??

[TUSC-AL]

Drove over Walton Bridge (surrey/middlesex) today. As I turned the bend on the Shepperton side, I saw a Police Vectra parked on the central diagonal lines facing my direction of travel. Mounted on the roof was a rear facing camera, pointing at either the bend or the other side of the road. No markings on the road - is this some sort of radar gun? Don't think i was speeding, passed the police car at 30, but didn't look in. Never seen this before...anyone else help??
Al.

[TUSC-AL]

forgive my ignorance, what's ANPR?

[TUSC-AL]

Just googled it - yep I think you're right, thanks.

[TUSC-AL]

that's the one...phew....