On personal observation I concluded that possibly:
Exclusive private local boys prep: 50% of my friend's boy's class are ethnic, predominantly Asian, there are no black boys.
Exclusive gils private school: 40 in the junior school, 2 are black.
Now these schools get their pupils into Harrow, Eton, St Paul, Godolphin, Westminster etc regardless of ethnic background. They are very good at it, however, the majority of children going are white or Asian.
State sector, black children represented as the typical % of population as you would expect, children shuffled into GCSE with poor advice, with an emphaisis on what subject they could get a high grade in to put on the school stats board not on what would get the child to a top university.
So black children are not a significant portion of the private schools who prime kids for top schools and universities, and then those in the state sector are channelled into easy to pass GCSEs for the school to get good stats, not for the child to get a decent university place. My neices were recently allocated GCSEs and my brother had to fight for them to be entered in the mainstream academic subjects, as he didn't want them with 5 GCSE ending in "studies" as he wants them to go for degrees.
Thus I think a great many students are being failed by the school system. If they don't study the right subjects and are advised against applying anyway, the likelihood is they won't apply. I'd prefer to see an article tracking the subject choices and attainment prior to application. I don't see how we can ever track those who were capable but didn't apply for one reason or another. But I do think the universities should not be blamed for a system that probably failed the children before they were 12.
The stats that would be significant would be: number of applications by ethnicity and gender, interviewees by ethnicity and gender. Selectors and interviewers by ethnicity and gender then a complete correlation...also across the whole of the university sector.
I think it would be worse if Oxford and Cambridge took people who patently would not be able to cope there. The only way they could do it would be to go on a big recruitment round to the careers advice services at schools and talk to 11 year olds directly. But they are not funded to do that, and they are already over subscribed, so there is no motivation either.