Before I ever wrote a book, I thought, like many people, that a plot/idea was what you really needed.

To a certain extent that’s true. I mean, you need to know what your story is otherwise you can’t write it. But I soon realised that as great as that idea might be, a book really needs a thousand more.

The idea of ‘boy goes to boarding school so he can learn to be a wizard’ could either be good or shit depending on how you do it. That ‘how you do it’ is the other thousand ideas: the characters of Harry, Voldemort, Hagrid and the others; how he gets to that school; the odd little platform at King’s Cross Station; Quidditch; the rival houses etc. etc. etc.

The idea of Quidditch is almost a book by itself. If I invented the idea of rollerball with broomsticks, I might decide to make a whole story about how it happens and all the stuff that surrounds the playing of it. JK Rowling (by the way, I’ve never read a Harry Potter book, but I did see the first two movies about ten years ago) is successful because something as inventive as that is just one of her thousand ideas.

You might have a scene where two people cross the road. What road? Which people? Are they talking? Running? Cartwheeling? The permutations are endless and you’ve got to have several ideas that you settle on just for that one tiny scene. Then you need more ideas for every other tiny scene, or big scene.

But up against the idea generation of advertising it’s a joy, partly because you’re doing it just for yourself, and partly because it’s up to you whether or not the ideas live.

Then again, you have to come up with the briefs yourself, every single time. And there’s much less collaboration, so if you don’t do it, no one does.

Over the course of a day, I like a bit of both. Swapping the pros and cons of either side can help keep you sane.

PS: I had a quick look at the ‘Best Places To Work’ supplement in the Sunday Times. I don’t recall seeing any ad agencies in there. Read into that what you will.