This was the first bit that I could find
Part 5 OPERATION OF AIRCRAFT
Operations manual
38 (1) This article:
(a) Shall, subject to sub-paragraph (b), apply to public transport aircraft registered in
the United Kingdom except aircraft used for the time being solely for flights not
intended to exceed 60 minutes in duration, which are either:
(i) flights solely for training persons to perform duties in an aircraft; or
(ii) flights intended to begin and end at the same aerodrome; and
(b) shall not apply to an aircraft flying, or intended by the operator of the aircraft to fly solely under and in accordance with the terms of a police air operator’s certificate.
Also Exemption from Low Flying Rules, page 288
(e) Police air operator’s certificate
Any aircraft flying in accordance with the terms of a police air operator’s certificate shall
be exempt from the 500 feet rule, the 1,000 feet rule and the prohibitions on flying over
open air assemblies and on landing and taking off near open air assemblies.