I suspect the UK security state has given safe haven to, and nurtured an extremist fringe of exiles from old style secular arab nationalist regimes such as Quadaffi and Assad, with the aim, always, of eventually undermining those governments. These elements would be, by definition, non-secular and fanatically violent. Now we are probably into the second and third generation of this particular strand of thinking - in the UK, among decent, creditable muslim-British.

I suspect this was, initially, another incident of classical blowback.

Predictably, it brought out an ugly British tradition on the right, combined with a summer tradition of rioting. Then everybody jumped on one side or the other - and the left (here for example) seems to have switched hats entirely from anti-imperialist to entirely identity politics, maybe not for the first time, even though both are elements fo this.