@AOG
First thing I think we should ask is, in the year where 27 were accepted, what was the backstory? That is so say(ask) how many applicants to begin with and how many applicants failed entry at the point of A-Level results?
Just to be sure that minorities were applying as eagerly as the "over-represented" group, you understand, not shunning Oxbridge due to it being full of 'toffs'.
Secondly, are we talking about substitution of "some" whites for "some" of minority ethnicities or an expansion in student capacity?
Important to stress this one because, in order to bump the requisite number of whites of the selection list, you have to raise the bar for entry standards to make them fail. And then the minorities entrants have to pass that raised standard, too.
The problem with that is, faced with wall to wall 4 x A* grade application forms, the only way you can grade them further is at interview stage.
If discrimination occurs anywhere at all, it's at the interview panel.