I go to Oxford not Cambridge but I assume the interviews are pretty similar. I was sent a case to read for one interview about a week before, you're allowed to have the document before you in the interview, which I only realised when the interviewer interrupted me as I was trying to recite the facts/judgement from memory lol, they didn't expect me to have understood the legal points of the case to a high degree and asked me questions such as what factors I think would be relevant to the decision (looking for answers like public policy, fair attribution of loss). Then I had another interview which was much less academic and was asked questions such as what I like to read for fun/how it has changed my view of the world, and what my most controversial view is. I spent about 5 out of the 20 minutes of that interview talking about Stephen King books. I was told by my school that it generally tends to be that if you come out of the interview thinking you've done badly, you've got in, and if you come out thinking it was easy and they loved you, something has gone wrong lol