I am frustrated by celebrities who decide to write children's books because they think it's easy. That drives me crazy. It's frustrating because it's unfair to children. Because they'll get a lot of attention, they'll get a lot of marketing budget and so on just because they're a celebrity - the Madonnas, the Ricky Gervaises, the Russell Brands.

And I have tried to forget him, I have tried to convince myself that it was just one of those things, but it’s difficult to do that when my body is standing here, eight feet deep in the earth of northern France, while my heart remains by a stream in a clearing in England where I left it weeks ago.

I like reading books about kids where there weren't really many adults, where they didn't need an adult to come and solve the problems for them. They could use their own ingenuity, use their own talents to solve whatever the issue was. And I like that still. I think that children want to read about heroic children. They don't want to read about children that have to be saved all the time.

It's not easy making a living as a writer, and for many years I worked at a Waterstones in Dublin. It was a good environment for an aspiring writer, with lots of events and authors appearing.

War today is such a more visible thing. We see it on television, on CNN. In 1914, war was a concept. There was a naivety and stupidity that war would be a great lark. It's not that different from Gone With The Wind, where all the young men can't wait to go off to fight and then two hours later in the movie, we see how the reality of that has come home to them.

... Nine-year-old boys usually turn ten at some point. It's the nineteen-year-olds who have difficulty turning twenty.

With the adult ones, I feel I need to get as deep inside the psychology of a character as I can, and that needs to be first-person. In the children's books, I feel I need some distance. I don't want to be the nine-year-old at the center of the story. I need to have some type of narrative voice.