Sixth Term Examination Paper (STEP); 2x interviews
Interview 1: unseen maths questions; Interview 2: discussion of pre-interview test questions
Practise challenging mathematics questions like Olympiads
Be willing to listen to hints and communicate effectively
Remember this advice isn't official. There is no guarantee it will reflect your experience because university applications can change between years. Check the official Cambridge and Oxford websites for more accurate information on this year's application format and the required tests.
Also, someone else's experience may not reflect your own. Most interviews are more like conversations than tests and like, any conversation, they are quite interactive.
Test taken:
Number of interviews: 2
Time between interviews: 1-2 hours
Length of interviews: 30 minutes
Online interview: No
In both interviewers, there were two people. An academic asked the questions, and a PhD student wrote down stuff about me (and sometimes they'd swap roles).
First interview was entirely maths questions. Questions were long, and only a couple questions were discussed and completed. It was actually a very relaxing experience, the interviewers very kindly told me to slow down when they saw that I was
Second interview was based on a 30-minute interview test, done just prior to the interview. There were eight questions that were semi-hard, and any holes in my solutions became points of discussion within the interview. I had given a proper go to only four of the test questions. The interviewers were incredibly persistent on the details, basically scrutinising my steps and asking "why" a lot, and helped me to correct my mistakes. Then they guided me through a question that I didn't attempt, from scratch. Again, they were very friendly people who were smiling a lot, and made me forget about the nerves.
Past papers were the most important thing for the
I had one
There are also some sample interview maths questions floating around on the Internet. Some are outdated, and probably wouldn't come up anymore, but it's all good practice. I think it's worth just doing a lot of challenging mathematics, wherever it's from, whether it be UKMT (United Kingdom Mathematics Trust) challenge papers, Olympiads, STEP questions etc. The actual content doesn't matter too much, just practise thinking about challenging problems.
I think of the interviews almost as a personality test rather than just another maths test. You don't have to be genius, you can make mistakes or head in the wrong direction (as I did in my interviews). As long as you're willing to listen to hints and can communicate with them effectively to get yourself unstuck, you'll probably be fine. Be teachable.