Is Oxbridge really that difficult to get into or not?

It also can vary according to college. My course is not that wildly oversubscribed overall, and interviews about 90% of applicants (or at least used to)... but I applied for the most popular college for my course, so was up against 12 other applicants for my place

Just for anyone reading this and beginning to worry, there is a robust pooling system so the choice of college shouldn't matter too much with year-on-year variation, especially after being called to interview.

It’s a very slight selection procedure, particularly since online interviews which have also been an excuse to cut interview times by more than half in some subjects (2 x 30 mins replaced by 1 x 20 minutes). So the prestige is highly exaggerated, particularly compared with prestigious but less well known institutions in other countries.
Which means that if you fancy having a go you have a decent shot. Not to say the system doesn’t work to some extent, but it’s a lot more ‘open’ than it was, for which you could read random.
My fear is that the online format favours the socially confident and the slick summary over the exploratory approach that used to be what was wanted. Certainly as well as its stand-out types, Oxford has a lot of self-confident ´averagely very good’ kids from comfortable homes, and feels less ´nerdy’ and more monied than when I was there (I have two children currently there). There is definitely a lot more conformism and wish to be ´ordinary’ than there was. At the same time the RG university where I teach has benefitted from an increase in exceptional but un-self-confident students. May just be a coincidence, and they are a joy to teach, so I shan’t complain!
Whatever, being accepted or not by Oxbridge should certainly not be seen as the test of being exceptional. There is a concentration of the exceptional there, which makes for an exciting atmosphere, but the majority are not, and have no wish to be, which is fine. And it has never been the case that the academics can necessarily be relied on to make the right call: many are excellent and conscientious, some are rather clueless, as my brief experience of being on a panel in the 1990s made clear, and confirmed by some odd (and some quite distressing) decisions amongst my children’s school friends.

By this I mean that often students (especially from lower social classes who are very intelligent) get overwhelmed by Oxbridge’s prestige and think that it’s impossible to get into. This may cause them to feel intimidated by their interviewers and mess up their interview or it may cause them to not apply in the first place.
But really is it that difficult? Assuming you have the necessary grades and you perform well on an admissions test and perform well in an interview are you then automatically guaranteed a place or could you still be rejected?
Has there ever been anyone with a perfect application who was rejected but there not being a clear fault or weakness in their application?

By this I mean that often students (especially from lower social classes who are very intelligent) get overwhelmed by Oxbridge’s prestige and think that it’s impossible to get into. This may cause them to feel intimidated by their interviewers and mess up their interview or it may cause them to not apply in the first place.
But really is it that difficult? Assuming you have the necessary grades and you perform well on an admissions test and perform well in an interview are you then automatically guaranteed a place or could you still be rejected?
Has there ever been anyone with a perfect application who was rejected but there not being a clear fault or weakness in their application?

I think the point about feeling overwhelmed is definitely true. I am a Y13 applicant and definitely do feel as though there’s absolutely no chance of getting in because of its prestige. From a social standpoint, I could not picture myself there at all.
But at the same time, there are a lot of other factors. Some of my classmates were encouraged greatly by their teachers and supported, so they had what I could call a false sense of security. Some of those people ended up getting rejected pre-interview. My sixth form lead told me I would get rejected pre-interview, and I did not. So of course, going into the interview was nerve-wracking because I felt like it would be wasting their time anyway.
Sorry for the essay. One more thing is that I think it is definitely much more than grades and admissions test scores. Last year, we had 2 applicants with a “perfect” application - top GCSEs, all A* predicted, top of their class, aced the admissions tests, had brilliant interviews, etc. Both of them got rejected. They were not even placed in the pool.

How can you be sure they had brilliant interviews?

"Averagely very good"? That calls to mind the politician who called for "every student to be above average".
Conformism appears widespread at most universities. Groupthink and tribalism seem to be the norm. Gen Z appears to be the least rebellious generation for ages. This may be the result of terrible educational policies since 1979, and the influence of nonsensical theories originating in French academies in the 70s, taken up by assorted charlatans in the US, and now accepted as the orthodoxy in many fields.
It seems to me arguable that in-person interviews might favour the socially confident more than online interviews.
As far as I can tell, it is harder to obtain a place at Oxford and other competitive universities than it was when I went to Oxford. I think that the Oxford entrance examination made the decision making easier for the Dons. Nowadays they have a mass of applicants with very similar credentials and there is little to distinguish one from the other. But the old system could favour privately educated pupils who could take the exams after A levels with teaching support from their schools.

By this I mean that often students (especially from lower social classes who are very intelligent) get overwhelmed by Oxbridge’s prestige and think that it’s impossible to get into. This may cause them to feel intimidated by their interviewers and mess up their interview or it may cause them to not apply in the first place.
But really is it that difficult? Assuming you have the necessary grades and you perform well on an admissions test and perform well in an interview are you then automatically guaranteed a place or could you still be rejected?
Has there ever been anyone with a perfect application who was rejected but there not being a clear fault or weakness in their application?

I never applied because I thought it was far harder to get in than it actually is and I think that must put many people off. It's a big regret of mine, I would really ignore you to just give it a shot.
Less than half the students at Oxford manage to get 3A*, obviously the average will still be high but it clearly isn't full of geniuses if half the students can't even manage that despite most people coming from private, grammar or high performing comp schools.
Obviously it varies by subject as well and stuff like CS genuinely does have insane competition.

Online interviews were so much less intimidating and better suited for introverted, socially awkward teenagers (such as myself). I specifically picked a college that did only online interviews for this reason. So definitely disagree that the online interview format favours socially adept students.
I think a big reason for this is that you do the interview in a familiar environment (such as your own home or school). Being at Cambridge during the open day was terrifying and made me feel very small and starstruck, as though I had walked into the wrong place.
Gen Z have a surprising diversity of views, but few are articulated online. A certain selection of views are broadcasted online as belonging to all of us when it most certainly doesn’t. But we are hesitant to degree. Because of social media, there is a lot to fear - for example, I don’t know if voicing my opinion on a certain matter may be picked up by someone who will be interviewing me for a job in the future. What if that person vehemently disagrees and this impacts their decision? Cancel culture exists. It might seem silly, but that’s that.

I never applied because I thought it was far harder to get in than it actually is and I think that must put many people off. It's a big regret of mine, I would really ignore you to just give it a shot.
Less than half the students at Oxford manage to get 3A*, obviously the average will still be high but it clearly isn't full of geniuses if half the students can't even manage that despite most people coming from private, grammar or high performing comp schools.
Obviously it varies by subject as well and stuff like CS genuinely does have insane competition.

If students at Oxford had more A* on average than they currently do, I would be wary of the reasons, e.g. if A Levels had become inherently easier to get a high grade. Oxford already don't interview as much as Cambridge as Oxford filter out people earlier using GCSES to a greater extent it is said, and always using admissions tests before the interview stage (whereas Cambridge may use admissions tests after the interview stage instead). If an average proportion of A*s more similar to Cambridge suddenly occurred, I'd be thinking that Oxford might be missing out on some distinctive minds just to robotically chase the crammers, who managed to eventually get A*s, in order to look good in league tables for average entry grades.