But when I reached secondary school, I realised Dad must have had an affair. Even though one survey reports that one in five British adults say they’ve had an affair, at a young age it didn’t occur to me that this is what happened. My realisation didn’t hit me all at once. It was more snippets of information, which had crept out over time and I ended up piecing together. For example, when Susan joked about Charlie having the loudest laugh as a baby, I realised the dates didn’t add up, as she wasn’t supposed to have known him as a baby, because he was three when she'd ‘met’ him.