I'm not involved in the interviewing process, but one thing any of my colleagues on the board will be asking himself/herself is "Do I want to be sitting next to this candidate in the middle of a six sector day?
If you've successfully jumped through all the hoops and made it to the interview stage, just try and relax and be natural.Easier said than done, I know, but remember we've all been through a similar "ordeal". Good luck.