I worked as a shift manager at a foundry in Darlaston and around 70% of the employees were South Asian. The hatred between the factions was palpable and fights often broke out over what we would call trivial matters. Even amongst the Hindus there was the caste system that created friction with the lowest castes literally treated like dogs. The Muslim factions also had a lack of religous cohesion with the Pakistanis despised by the Bengalis and vice versa. Everyone had no time for the Yemenis!!
I think the issue has been latent with all factions coming together to fight inequalities and now that that seems to be reducing, the deep seated tensions are coming to the surface.
The most disturbing thing is that if you look at the video of the troubles, the men involved appear to be teens and twenty somethings and were born in the UK - probably 2nd or 3rd generation - and you would think that they would know better.