1x test (in advance); 2x interviews
1st interview: pre-interview reading; 2nd interview: personal statement
Reading around subject & other humanities
Don't be scared to ask for clarification
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 - the first one was based on a reading, and the second one was more general. There was a HSPS
In between interviews, I waited in the buttery with other candidates. I also stayed in the college the night before because it was an early morning interview and I flew in from Singapore the day before.
The interview based on the reading - started with what I though were the main arguments of the article. The reading was an extract from the introduction of a book. We discussed whether I agreed with the article. The rest were follow up questions which I can't remember much of.
The second interview asked me about a book I mentioned in my personal statement, and how I thought it related to modern-day politics. She also asked me something about British politics and when I said I didn't know much about the structure of the British government, she gave me a two-three sentence answer and then asked me to try to answer the question. My last question was about what kind of research I am interested in.
Regarding the aptitude test - all I remember is the first section was multiple choice that corresponded to a series of readings that had barely anything to do with HSPS. It was mostly comprehension. The second section had a list of essay questions and I had to answer one of them - it was easy to tell which questions were for which discipline - Politics, Sociology and Social Anthropology.
I picked one or two ideas that I would try to fall back on - and prepared the gist of what my position was and some examples. I tried to read around it - but not too much because I didn't want to encourage them to ask me about something I brought up and then realise that I hadn't read enough to answer them. I did History in IB, so I decided I would draw examples from there because I knew enough about them from revision - but it was useful to prepare how to change a history-style answer to an answer about politics or sociology.
It's perfectly fine to ask them to clarify their question or to admit that you didn't really know what they're referring to. I think they like to throw you off or see how you respond to brand new information to test your analytical skills.