Sorry Slacks, but I'm going to disagree with you, slightly. If he is a bad interview, he may never get a HC job and it's really nothing more than that. It's not reasonable to expect to ever be the face of a billion dollar operation if you can't make it through an interview with the people who will be your bosses.
A couple of side stories, one of my buddies asked me to meet a woman that was interviewing for a job where I worked. Foreign language skills were such a plus that you would almost be a shoe-in if you were a half decent speaker. She knew French. So I meet her for lunch and I'm giving out some pointers that the interviewer will likely be looking for as well as what I know about the job and the company. At one point I ask a question about how she was preparing for the interview, she responds with "Oh, I don't want to be over prepared". I tried to be as helpful as I could, maybe I should have said what I was thinking. "I DON"T KNOW WHAT OVER PREPARED IS!" But I didn't and I doubt it would have helped. She wasn't over prepared. All I heard back was that she didn't get the job.
A while back, a guy comes in to interview with us where I work. No suit, wrinkled shirt, unshaven, missing some documents that he was supposed to bring. Still had an attitude, something like -I'm so qualified/deserving that NOTHING else matters and I'm a shoe-in. Claims that his suits/documents were in his car that got flooded down in Houston (reasonable, since the flooding was recent). Still no reason you couldn't shave, iron your shirt and drop the attitude. I can't remember what the starting pay was, but it pays $200- $300K by year three, live anywhere you want, 12-18 days off a month, pretty sweet deal. Yeah, he didn't make it either despite the company being desperate to fill the position.
Probably too Freudian, but if you aren't willing to do everything within your power to show well in an interview, deep down you don't want the job or doubt your abilities and it's best for everyone involved that you don't get hired.