Protestors assemble with banner
An angry demonstrator.
Police assemble to give warnings
Leaflets are handed out
Police decline leaflet defining the limits of their powers
Man is separated from his banner and arrested
Police permission refused...
A squad of around twenty then moved in and gave individuals verbal warnings, prior to snatch squads removing them to waiting vans.
It was apparent that they had targeted demonstrators with banners - the act of separating protester from banner seemed to be part of the theatre. Several people announced they'd be back next Sunday with banners in tow, a fact quickly noted down by eavesdropping officers.
More demonstrations are scheduled in Parliament Square, check Protest.net for details.