I think the important thing is that there is no question that many intelligent and capable people don't go to university, and many who do go are there because they were tutored or went to schools that concentrated on exam results.
When it comes to employers, there will be those who want a good 'fit', and yes, in certain occupations and companies only candidates from public school and Oxbridge stand much of a chance of getting an interview. Not fair, but this is the UK, and snobbery is endemic.
On the whole, though, graduates have the edge when it comes to entry level jobs, for the reasons I described above, but after a few years a weak graduate is unlikely to have progressed very far, whereas a good school-leaver might have shown promise and climbed the ladder, so the playing field is levelled a bit. It is never easy to play catch-up, so the graduate will have an easier time, but this is because they are less of a gamble to an employer than a school-leaver, which I think is understandable. It's by no means impossible for others to end up doing equal or better jobs though, as people have shown in their examples on this thread.
It may not be 'fair', but equally, it isn't fair that some people get jobs because their dad's friend is looking for someone, but that happens too.