i've had one, and it's just simple questions like where were you born, addresses you have lived at, companies that you receive post from etc.
I will warn you now though, these people do not have a sense of humour!
You must take this interview totally seriously!!!
And something else, do not go there early or they will not let you out!
I popped in, in my lunch hour because I couldn't remember if my appointment was 2:45 or 3:15, but the receptionist replied "unfortunately now you have entered the building, I cannot let you go or you will have to reschedule for another day".
It's like a military operation....hope I haven't scared you too much!
Paul