2x interviews (30 mins); test (45 mins)
1st interview: source; 2nd interview: document
Reading a book
Be honest
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 2 interviews in one day,
In the first interview we discussed my motivations for studying History and they also showed me a picture of a painting I'd never seen & asked me my thoughts on it. Never having seen it before, and not really knowing what kind of thoughts they wanted, I stumbled a bit, but outside of that the interview went great - I didn't think I had a chance so I was really relaxed oddly enough.
In the second interview they asked me questions about the document I had to analyse, and also about my motivation - I basically gave a lot of similar answers than in the previous interview, basically all the answers which seemed to go down well I repeated.
Honestly the most important thing I think is that, not thinking I had a chance, I was going in to spend 20 minutes with proper Historians, an experience I had never had before and didn't think I'd get to experience again. So I must have shown my curiosity and interest through the questions that I asked them about the history of what they were asking me about. If I didn't have the answer to a question, I wouldn't try and bullshit my way through - I'd say "I don't actually know anything about that - but what is it? It interests me".
I was left pretty much alone for my preparation honestly, so all I did was read 1 book a teacher has lent me on Napoleon. That's it.
Don't bullshit! It shows much more to say "I don't know about that, what is it", than pretend you know. It shows much more to say "I'm not very good at (...), but I think that studying here will make me better at it" than "I don't think I have any weaknesses".