very informal chat, almost like a meeting with someone you know just discussing issues. the guy even went and got us both a coffee. I would say act very professional, i know we always do but act even more professional than you normally do. Buy an expensive suit so that you fit in. Always look your best, seems like a cook place to work for, although the interview process is a little bit stranger than normal. they are asking successful people to go back in to solve a problem, however would not elaborate on what this is in any way