The interview stage in the Oxbridge admissions process is perhaps the most notorious of all on the road to university. However, this is needlessly so. There are some simple academic and non-academic preparations that every candidate can do to ensure that their interview is as strong as possible.
The first is to know your relevant A-Level course(s). The interviewer cannot expect a candidate to know any super-curricular information. All that they can expect is comprehensive knowledge of the relevant A-Level courses to the point that they’ve been taught and the ability to apply that knowledge to unfamiliar contexts. Any questions that are asked will only entail skills covered in your A-Level course. The only exception to this may be if you mention more complex concepts in your personal statement, which leads me to my next point.
Know your personal statement. Often interviewers do not dwell on one’s personal statement too long. However, it is common that at the beginning of an interview, in order to make the candidate feel more comfortable, a few ‘loosener’ questions are asked on their personal statement. Slick answers on these are unlikely to score you many points, but you can certainly lose them as not being able to move past this section of the interview relatively quickly makes the candidate come off as unprepared and means that the interviewer cannot ask as many questions later. If, for example, you have referred to any super-curricular topics or books you should understand them to a reasonable degree so that they can be covered easily and allow you to move on and shine in the main section of the interview.
This being said, acing an interview is not all decided on your knowledge, even if it seems that the university only care about your proficiency for the subject you intend to read. Of equal importance is being passionate about the subject. Tutors are not just looking for someone who already knows everything there is to know, but also someone with a mind they can shape and who has genuine interest. Studies say that only 10% of communication is verbal so, when being interviewed, body language is incredibly important. Smiling, keeping good eye contact, sitting up straight and looking interested all can differentiate between a successful and an unsuccessful interview as well as making you look more humble and teachable. Coming across as arrogant can massively hinder your chances so maintaining a good attentive posture/body language will work in your favour.
Remaining calm is key as the questions you are asked will likely be unfamiliar. If you are asked a question which is outside your field of knowledge, take your time and think about the question you have been asked carefully. Interviewers want to see your thought process, so let them know what you’re thinking by doing so out loud, so they can direct you accordingly. The interviewer is there to be helpful and should guide you in the right direction if you are struggling, so listen to their hints, and try again. Any answers you give should be justifiable logically so try your best to show an understanding of what you are being questioned on and why. Do not be perturbed if you are struggling or do not understand the question – simply ask the interviewer to repeat or elucidate.
Although these are by no means steadfast rules, this is what I picked up having gone through this exact process and talked to my current tutors about it. At the end of the day, no admissions process precludes an aspect of luck and so all I can wish you is best of it.