2x interviews (20 mins each), 1 day apart
Progressively more difficult questions about concepts
Past papers
Revise personal statement; contact current students if possible; practise interview-style questions.
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
Skype interview: No
Time between each interview: 1 day
Length of interviews: about 20 minutes each
Every interview had the same format. They introduce a concept to you and just get you to play with it then see how you react.
They then asked progressivey more complex questions about the effects of changes to the concept they had introduced until I couldn't answer.
I completed a couple of past papers.
Revise your personal statement,
I found the interviews as I had exppected - a little baffling at points but, having practiced questions with friends and