3x interviews (15 mins each)
Discussed different scientific concepts and interacting with patients
Read topical news stories.
Explain your thought processes to the interviewer.
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.
I had 3 interviews, each with one interviewer, and I think 15 minutes each. One was clinical, one was chemistry based and one was focussed on problem solving.
We discussed some problem solving questions, then about interacting with patients and esterification.
I read science news articles in the week before the interview, to make sure I was comfortable with any topical science questions they asked.
The most important thing for me was explaining any thought process one did to reach an answer to a question.