Oddly enough, despite a massive police presence and the police commitment to recording as much of every demonstration as possible for future reference, evidence of these incidents surfaced not on any official recording, but on film shot by passers-by.
Readers with longer memories may remember how a similar effect appears to have affected official cameras around the time of the Stockwell incident, in which police marksmen shot and killed innocent Brazilian Jean Charles de Menezes. According to the police, CCTV footage that might have shed some light on events apparently never happened, or was wiped shortly after.
We could go on. There is the incident outside the Greek Embassy last December, in which a policeman in no uncertain terms interferes with a photographer going about his job. There is the incident reported yesterday, in which an Austrian tourist, Mr Klaus Matzka, appears to have been made - unlawfully - to delete shots of a bus station. Or a little further back, this footage from independent film-maker Darren Pollard in Birmingham shows that police secretiveness is not restricted to the Met.
In connection with this case, a spokeswoman for the West Midlands police said that as no formal complaint was received at the time, no action was taken. She added: "Police Officers receive training in the Laws of the UK when they are first recruited, and are sent on regular refresher courses throughout their career."
This is similar to responses we receive whenever such an incident comes to light. We have also heard from serving officers who are beginning to spot the pattern and are very worried about what all this is doing to public confidence. One view they regularly express is that part of the problem lies in the increasing formalisation of police-public encounters.
Whatever the precise reasons, our own sense is that a tipping point is being reached. Police excuses are wearing increasingly thin. If the issue is not addressed soon – as the systemic problem we suspect it is - then the police will only have themselves to blame for a massive loss of public belief in their integrity. ®