The Met have issued "Guidelines" regarding photography:
http://www.met.police.uk/about/photography.htm
It covers not just the use of the new law (Section 76 of the Counter Terrorism Act 2008, which amended the Terrorism Act 2000 with Section 58a) regarding photographing police officers, but also the use of Section 43 & Section 44 of the Terrorism Act 2000.
Telegraph journo Kate Day has blogged about it:
http://blogs.telegraph.co.uk/culture...hotograph-who/
Apparently the Met's advice is not Home Office approved:
http://www.amateurphotographer.co.uk...ws_285926.html
Another article at The Guardian:
http://www.guardian.co.uk/commentisf...sm-regulations
It includes some examples of Section 76 being used to stop photography of the police.
It also has a link to a blog post by someone who was arrested (& later eventually "de-arrested") under Section 44 after taking photographs in Chatham High Street:
http://monaxle.com/2009/07/08/sectio...m-high-street/