I spend most weekends in South Norwood and surrounding areas, Croydon, Thornton Heath, Selhurst, Crystal Palace etc. You are right there are a number of immigrants/Asylum seekers that have come from a culture where black people are considered second class citizens. Racial tension is there. I haven't seen any evidence of the other tensions you mention but hey that's just me, you obviously have.
You're spot on there. Africans normally seem to cop the brunt of it.
My own personal experiences are wide ranging, and are based solely on either working with people/small companies in the SE London region, or through knowing friends & family who have lived there. I've witnessed the racial hatred from one minority group, towards another minority group, first hand, on hundreds of occasions, through personal conversations.
Just off the top of my head; I've had Portuguese in Camberwell openly refusing to work with/for Africans. Chinese in Deptford, refusing to work for/with Africans, unless certain stipulations are agreed. I've had Eastern Europeans in Sydenham, refusing to work with/for Africans. I've even had British-born black people in SW8, tell me they're embarrassed about some Africans behaviour, because it reflects badly on them.
But on the flipside, I've had Africans, refusing to work with/for Asian's, such as Pakistani's/Indians etc. I had one Jamaican guy in Walworth, tell me he'd rather shut his business down, than work with Eastern Europeans. And then of course, there's the Pakistani Muslims in SE7, who point blank refuse to even acknowledge Jews, because apparently Israel is in cahoots with India, to destroy them, or something nonsensical like that.
And that all pales in comparison, to the racial divide between the Asian Communities, which of course dates back over the decades. Ive had Punjabi's in Bermondsey, telling me exactly what they think of Gudjurati's, and believe me, it's nothing complimentary.
So if I can try and drag this thread back on topic, my origional post was in response to Barna's link, that Racial tensions were on the increase in London. My point is, these tensions are very much there, but IMO, it's mostly stemming from interhouse immigration, than from people born here. Which, again just IMHO, is down to poor integration, and ideaologoes that don't fit what we class as British Values.