Sixth Term Examination Paper (STEP), 2x interviews
Interview 1: set of unrelated questions Interview 2: linked questions but on varied topics
Practice at problem-solving and at talking through it
Practice working through STEP-style questions (especially from STEP papers), and graph sketching
Practice talking about maths and dedicate lots of time to STEP
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: Sixth Term Examination Paper (STEP)
Number of interviews: 2
Time between interviews: 3-4 hours
Length of interviews: 20 mins
Online interview: Yes
One interview was a random set of unrelated questions.
The second had a few which linked, but topics were varied across the whole syllabus.
It's very important to develop the skill of speaking through your work, it's hard for the interviewer to know what you're thinking if you don't explain it and speak. This is especially important when you are presented with Mathematics that you are not familiar with or that you get stuck on - they will know what you are thinking and what they need to hint you towards in order to help you to get to the answer.
I prepared with
Don't look at answers or other solutions - the whole challenge with hard maths/STEP is developing the skills of being able to succeed after you get stuck. There is no benefit in giving up straight away because that will not be an option when it comes to the real exam, you need to practice sticking with it even when you feel completely stuck/hopeless (everyone who does STEP gets to this point!).
Any STEP practice is good practice so don't overthink the work you're doing, just try and do as much of any STEP revision as you can. It's a long road to becoming good enough for the day of the test and will take lots of hours. Please practice graph sketching, it is the single most helpful skill (in my opinion) for STEP and technical maths interviews.
Practice answering interview questions in front of someone else (even if they do not understand the maths). Spend a lot of time on STEP and make sure this practice is spread somewhat evenly across Year 12/Year 13.