I'm sorry, this is just not true.
20 years ago, a brown or black person wouldn't have gotten anywhere near high office in the UK (or anywhere across Europe), regardless of what school they went to or how much money they had. The number of ethnic minority mps in the 2001 Parliament was 12 (across the whole Parliament), it's now 65.
Just had a perusal of the 2001 cabinet to remind myself, it's a who's who of old white people, mostly men. In fact, I don't think there was a single ethnic minority in the cabinet in 2001 at all.
That doesn't mean that their policies aren't more aligned to mine than the tory party but it's not exactly difficult to see how a 16 year old Sanjay in 2001 may look at politics and say....probably not for me, I won't be accepted. That can be the case whether Sanjay was educated at the shittest comprehensive or at Eton, Oxbridge and then Harvard, with a billionaire dad. Because that person didn't exist in British politics, essentially at all, let alone in the actual important offices of state.
That is no longer the case, whether those people in the offices of state are cnuts (they are) or whether you happen to agree with them or not (I don't).