The police in London were trying to maintain law and order on the streets close to our seat of power and a number of high-profile targets (buildings, monuments and individuals). From what i have seen (ironically from media posted by people trying to spin it otherwise) they came under sustained and inexcusable attacks from pissed-up racist (or at least xenophobic) thugs, and took appropriate action, including kettling to effect arrests of people who had committed offences.
As for the riots in Leeds and Southport, the police took the same course of action to contain the rioters, so this bollocks about "letting the Muslims get away with it" in Leeds, while clamping down hard on "patriots" in Southport is just that.
Hartlepool is just monkey-hanging territory and a law unto themselves!