How much research do you need to do for your novels?

My research is two-fold. First, and obviously, I have to research the details of daily life (which, admittedly, I seem to find hard to retain! I have to go over it again – what people ate, what they wore, how they spent their days – for each novel). Secondly, I’ll read as widely and deeply as possible on a character, weighing up the various historians’ accounts to try to reach an accurate picture of him or her. That’s very important to me; I know that my job as a novelist is to make things up, but I do try to stay true, as it were, to the real people.