Imo, no.
Academia has no skin colour, it's about hard work and ability. If I was an admissions tutor and I could only accept 5 out of 100 candidates, and if it just so happened that the only two black candidates didn't give a strong performance in interview, it would be fair to reject them, had everyone else's interviews been stronger. That has nothing to do with race, it is to do with academic ability and response to my questions/pre-reading etc. In my opinion, quotas shouldn't be set in place because it will only focus on diversity rather than equality. Insisting an obligatory 20% quota of black students for every course takes the focus away from the black students' work and it will mean they got in because they were black. From the other side, it will hinder the other applicants' chance of getting an offer, and that links back to what I said. If in a specific situation, the only black students of the lot didn't give strong performances in interview, then it is only reasonable to reject them. Just like if a white person in this instance didn't give a strong interview, it would be perfectly reasonable to reject them. The focus on diversity in academia should be set much earlier. Given black people in the UK tend to be poorer, especially in London, there should be more done in primary schools and secondary schools to make not only black people, but any group, aware of what they could go on to do. Both of my sisters are strikingly intelligent, A* grade students, and one of them was accepted into Oxford for Maths and is now in their 3rd year. We are mixed race (Afro-Caribbean and white British), and my sister wasn't accepted because she was mixed race, but she realised her academic potential at an early age. Now, speaking of being poor, we are even poorer than everyone in London, we're from the North East and were state school educated (my sisters earned scholarships at a local private school). Anyway, I've rambled on a bit, but the point is, no, don't put diversity in place now! Put it in earlier in life!