I’m sure that there are many ways to mess up an interview and not turning up would probably be high on the list but recent experience would point to some not quite so obvious ways:

Not answering the question put to you would be high on my list. If you don’t have the exact background required and maybe your experience is from a different sector, in my opinion, it is perfectly alright to respond to a question with a answer that begins something like; “Well, I don’t have any direct…