You do see a few people and you are thinking of how that chemistry is going to work, but it's not really fair to put people who are auditioning together in a room. You have to make that judgement yourself, and that's partly where the casting director is so good. It was that blend that we were looking for.

One of the problems of this genre is that there are cliches everywhere, and you've got to be careful and watch out. Our rule with cliches is to either gently acknowledge them and make fun of them, or do something else. Milady is, in one sense, a villain because she does bad things.

In the book, D'Artagnan doesn't actually become an official Musketeer until quite near the end, and we make quite a big thing about that. I won't give too much away, but when he finally does make it, they're not going to make it easy for him. That never changes.

It's not fundamentally different to any other genre, that action is a particular thing. Being able to do action sounds like it should be straightforward, but it really isn't. I always want the action to be witty. I don't want it to be merely routine.

On a simple level, you need directors who are good at action and can choreograph an action scene, but you need them to also have that sense of fun and that sense of movement and that ability to get the actors to really respond to the material in the way that you want them to. It's a very big thing.

The BBC came to me and they wanted to adapt the book [Three Musketeers] again, in the straightforward way, and I said no to that. I didn't want to do that. But what I did want to do was have a real look at the adventure genre because I thought it was ripe for reinvention.

The situation that women were in, at the time, was something that Dumas doesn't really go into, but it's a great subject to look at. It's a great genre because you can do a lot. Sometimes in thrillers, you can really explore things, and it's the same in this genre.