2 x 25 minute interviews. First was maths based, second was about chemistry.
First interview about graph sketching and differentation. Second about A-Level chemistry content.
Practice interview with maths teacher.
You have no way of telling how it went afterwards. Oxbridge isn't always the best option.
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 two interviews in December, spaced 10 minutes apart. I am from Norwich so I got the train up on the day and went straight back home afterwards. I made my own way to my interviews and don't think I really interacted with anyone from college. Each interview lasted about 25 minutes and there were two interviewers in each interview. My first interview was very numerical and the second one focused on Chemistry.
The first one they asked me to sketch graphs, differentiate and then asked me a weird question about quantifying the information in a grid. There was very much a good cop/ bad cop set up which was a bit unnerving. The second one was much more relaxed, and much more focussed on chemistry content from A levels. They asked me an outside-the-boxc question about testing compounds on a space ship and then a pretty standard question about equilibria. Afterwards I honestly felt pretty bad about the experience, especially the first interview.
I had some pretty nasty
There is absolutely no way of telling how it went so don't torture yourself afterwards! Also Oxbridge is not the be all and end all, there are lots of cons to the pros and it may be that a better balance can be struck elsewhere.