It was a seriously intense assessment day- it lasted 8 hours in total- and I was interviewed alongside everyone who had applied for the HR grad scheme, despite only going for the summer internship myself. There was a personal interview, maths and writing exams, a group project and a technical interview. Despite this, everyone there was really nice and the day was very well organised; the interviewers were very friendly and despite having never done an Assessment Centre before, I wasn't as nervous as I thought I'd be. Just make sure you've researched the company as they ask you about it loads.