I always used to think Agatha Christie was a good plotter of thrillers - a good writer.

Then one day someone pointed something out to me. The reason its so damn difficult to spot who the murderer is, is that they are not real characters - they are stereotypes.

A good writer writes proper characters, whom you can imagine sitting down with and talking and you will be able to guess some of their opinions - and what it feel like to be in their presence.

Sydney Carter was not a stereotype. His character had no elements in it that would consider harbouring the criminal intention of which you accuse him.