I know someone (white, working class) who got into Cambridge years ago via an entrance exam/interview despite A-level grades of A, B & C. They attained a 2:1 degree, so they were obviously academically capable once given the opportunity. I'm not sure if they would get in nowadays, but maybe that's a different discussion based on state vs private school quotas?
On the subject of Jason Arday, it's incredibly tragic that his story has ended this way. I can't help but feel that a degree of blame can be apportioned to many of the parties involved, no matter what 'side' they're on. Of course Arday himself was the architect of his own downfall, but those who enabled and encouraged him in his delusions without doing due dilligence are also culpable (especially Cambridge University). It shouldn't have come to this, but the press and public scrutiny he faced did feel disproportionate at times, especially when compared to someone like Jess Taylor, another fabulist who is far more harmful to the wellbeing of vulnerable people than Arday ever was imo.
I think he compared himself to Icarus in one of the flights of fantasy in his florid autobiography. Seems like it was a self-fulfilling prophecy in that he chose to fly too close to the sun and was ill-equipped to deal with the heat it brought him.
His is a cautionary tale, but unfortunately I feel it's more likely to lead to recriminations being flung around rather than actual reflections by those who could and should have dealt with things better.