If you haven't been to an assessment day before then it is scarier than everyone else says. We started by having to introduce ourselves in front of everyone (+ the managers&executives) and basically had to sell ourself. Then in film we had a speed dating session where they asked questions like 'what type of biscuit would you be'.
After this we watched the current interns do a presentation about their work with some little video clips. For Film we then watched a recent trailer and had 30min in allocated groups to present our marketing plan. For TV we had to build to POS stands, complete a questionnaire and present a marketing plan for an upcoming TV launch. (Personally this is not a good judge of character - we all share ideas within a group but it seems to be that you are basically competing against the others in your team).
Then we had lunch, this is when you 'mingle' - this is a vital part of the day. I felt as though they are just looking for people they would get along with or are obsessed with TV/film. You should be yourself but don't let people over speak you because they will get the interview and you will go home.
After lunch out of 20 of us 6 stayed and all the rest were told to go home. No feedback at all.