I'm never going to believe a Poirot mystery again. Never. All those witnesses going, "Yes, I remember it was 3:06 p.m. exactly, because I glanced at the clock as I reached for the sugar tongs, and Lady Favisham was quite clearly sitting on the right-hand side of the fireplace."
Bollocks. They have no idea where Lady Favisham was, they just don't want to admit it in front of Poirot. I'm amazed he gets anywhere.
