Well Nick that all depends on what you don't care about.
In my interview for Virgin I just relaxed and was myself-- I didn't care about impressing the interviewers I just went in to have fun and be myself. Well it worked.
I'm guessing that because I came across as natural and just looked as though I was enjoying myself I was more the person they were looking for!!!
So as long as you know your stuff and are confident- I believe that if you 'don't care' about impressing anyone and you are just yourself then you may hit the jackpot!!
Good luck
love SMILE