Hi, sorry if this is too late.
My first interview i thought was quite informal and was more like an hour long chat. Basically they will go through your application and ask two or three specific questions from this such as why did you go chose your degree etc. They will also some pretty standard questions about your motivation for the job etc. One thing I would learn is the competencies that are listed on their website as they will be looking for you to mention these at a certain point. And have some previous examples of when you have used…(standard competencies for interviews, such as teamwork etc) as these may be asked and will also be if you have the second interview.
The AC format was an introduction by everyone, a group exercise, a logic exercise with cards, lunch with trainees, a presentation on the group exercise and finally a partner interview. The cards test I was told is the least important part of the day and took the least time- they said that they would only really look at the results if there was two exactly matched people by the end that were going for one job. I wouldn’t worry about it though as there is no real prep you can do and its just using logic to figure it out.