When I tried to answer this based on the job spec and what the agent had told me, they all pulled pained expressions, one shook her head and when I suggested that since my answer was clearly wrong they explain it to me further they told me that the role hadn't really been defined yet. They were still trying work out what it might entail. They were just meeting people to see if they liked them. What a waste of people's time! I travelled across London for what amounted to little more than a personality contest. If you decide that the role has changed then fine, just don't make the candidate feel bad for not being telepathic. If it's going to be an informal chat then say so, don't pretend it's a formal interview.