Well mine only lasted around 15 minutes, was with my personal tutor and Paul Reading who is now head of dept. They asked me what books I'd studied for my English Lit. A Level and when I said Pride and Prejudice they asked me a few questions about that. Examples would be 'Did Austen display feminist traits purposely or is that what modern readers have taken from her?', 'Why do you think Austen rarely mentions important events happening during the time her books were set? ie wars, and if she does only in a rose-tinted light?' and something about portrayals of masculinity/femininity. Then they asked me what I'd studied for my history A Level and asked me some pretty basic thematic questions about that. There was never any right or wrong answer, they seemed genuinely interested in what I thought about the things I'd studied, and both told me what they thought too. They asked what periods I'd like to study and why (Because I knew who was interviewing me I made sure I mentioned both of their subjects, which went down well, and I wasn't lying anyway!). That's about it, just asked me what attracted me to King's, what I do in my spare time and what I hope to achieve through a history degree.
It wasn't very formal or scary really, much better than I expected.