I applied online which involved me answering some questions - some were the classic competency questions that are commonly used for undergraduates, and others were specific to the role and required some research.
I then was invited to an assessment day in London. We started the day off with an icebreaker: name, university, degree programme, and what Warner Bros character would you be and why (try and avoid using the classic superheroes, as it's very likely others will use this as an answer and you won't stand out).
Next, we had to complete a group task with a presentation at the end which was pretty straight forward, it was just an opportunity to show how you work with others etc.
Then, we performed an individual presentation on research we were required to conduct prior to the assessment day - the assessors complimented my presentation on more than one occasion, so based on what I did I recommend not to use a script - try and be as natural and engaging as possible. Also, I think it's best to focus on one idea / aspect in-depth, rather than a few ideas with little detail. Also, really try and relate the research / task to the job as this is what will impress the assessors.
After the assessment session, I was invited to stay for an individual interview with 4 other candidates. The interview was very relaxed, all the staff was friendly and approachable - something I noticed from the beginning. The questions were centred around my CV with the occasional competency question. Unfortunately for me, my nerves got the better of me, so I recommend focusing on being confident, bubbly and enthusiastic - try to not let the nerves show, even if you are really nervous!