"When I created Quirke, he was 6ft 6in and blond. But then a woman reader wrote to me and said, 'Why do you keep saying his hair is blond? It's not. It's brown.' I wrote back to her and told her that, of course, she was right. So I darkened his hair and now that he's being played by Gabriel Byrne; with each successive book he gets a bit smaller and smaller."