In fact, writing for younger adults is tougher. They remember everything and if they spot a problem, they'll be sure to let you know.

Negotiations are about controlling things, about being in the driver's seat and make one tiny mistake; you're dead. I made one tiny mistake, I wore women's clothes

But magic, like everything else, follows certain natural laws. Magic needs energy wherever it can find it. If no other source of energy is available, it will take the life force of the magician who created it. That is why every use of magic weakens the magician.

I published my first book in 1982 - a collection of Irish folklore called Irish Folk & Fairy Tales. It is still in print today. My first young adult book was published a couple of years later, and I've been writing in both genres ever since.

So you should be able to see them clearly in your imagination. We always find it easier to visualize what we fear; it's what keeps us afraid of the dark.

The research. It is always the best part of writing. And, of course, it is the great excuse to travel.

Research is always the best part. As we dug deeper into the history and mythology behind each of the hallows, we discovered more and more stories - some of them deserving of novels in themselves.