I had a terrible interview at Cambridge in the 1990s, and didn't get a place.
This will out me to anyone who knows me...
It was completely the wrong place at the wrong time. I'd left school at 16, spent a year in and out of hospital, working various jobs, had moved out of home and was then going to a sixth form college and living with my (then in his late twenties) partner, who drove me there to the interview.
I was very very bright, but also very messed up, and had no idea of how posh/formal it would be. I went wearing my normal 17-year-old garb (tight t-shirt, combats, army boots, nose ring!) and as I was waiting for the first interview I could hear the previous girl smarming up to the interviewers about how much she loved the King's College Choir every Christmas. I was more into the Chemical Brothers and the Manics...
The interviews themselves I found very frustrating. They were obviously designed to be challenging but I could see that they were just trying to be annoying for the sake of it and it wound me up.
(For example, I had expressed a liking for Shakespeare. They asked which plays I knew - I listed about 10-12. They asked how on earth I could say I liked Shakespeare when I only knew that many. I just thought that was so pointless and irritating. Like I say - not the right time or place for me!)
They would also have made me live in the college, apart from my partner - by then we'd been living together for a year and been through a LOT (he had cancer) and we were each other's rocks.
So I knew I didn't want to go. I'd made that decision by the time I left Cambridge that day.
I was hella relieved to get the rejection letter, because I'd been agonising over if - if I got in - I should be honest with my parents and say I was turning down the place, or if I should lie and pretend I'd been turned down. So it was good that the decision was taken from me.
In the end i went to another, very good university, where I had the most brilliant time, got a First, ended up doing a Masters and a PhD there, made some lifelong friends and ultimately met my now-husband. Everything I found out about Oxbridge subsequently made me very glad I didn't go there. I've always felt like I dodged a bullet.