Jim wrote:
Do the Congestion Zone cameras in London take pictures at times other
than the charging period (7am to 6pm, Mon to Fri)?

I was discussing with someone who felt they might be left switched on
and recording to keep an eye on criminal, terrorists, stolen cars, etc.

Depends what the CCTV license states the purpose is for.

If the license (or whatever it's called) states that it's for traffic
charging only, then they can't use it for ANPR etc.

D