Well, yes, no, I certainly visualise … it was really … I had to have a very good idea of the geometry – that was crucial. Spacetime geometry so it's not three dimensions, you have to think of the whole four dimensional spacetime, and I get sort of used to thinking about four dimensions and using various tricks to get the picture properly. I do most of my thinking in visual terms, and I'm a very visual thinker rather than writing down equations.

But if I’ve come up with any kind of mantra for myself it’s to try and put myself into a state of imaginative play.

I just like to get to the start line knowing there was nothing else I could have done, that there wasn't a single session I didn't give 100 per cent. The physical certainty means you can relax mentally and let the performance come.

I love training. It's not just about the competing. I had an amount of natural talent – you need that to go so far – but, actually, what I had, I think, is an ability to make myself work hard, to do the things I didn't like doing, to do the things that I wasn't so good at.

So far they are conforming to pattern, alas! I mean I am suffering from the usual delusion that the play was ready before we went into production. It happens every time. I give my publisher the finished text of the play so that it can be published not too long after the opening in London, but by the time the galleys arrive they’re hopelessly out-of-date because of all the changes I’ve made during rehearsals. This time I gave them Hapgood and told them that it was folly to pretend it would be unaltered, but I added, “I think it won’t be as bad as the others.” It turned out to be worse. Yesterday I realized that a chunk of information in the third scene ought to be in the second scene, and it’s like pulling out entrails: as in any surgery there’s blood. As I was doing it I watched a documentary about Crick and Watson’s discovery of the structure of DNA—the double helix. There was only one way all the information they had could fit but they couldn’t figure out what it was. I felt the same. So the answer to your question is that the rehearsals are going well and enjoyably, but that I’m very busy with my pencil.

I don’t think of it as research. I read for interest and enjoyment, and when I cease to enjoy it I stop. I didn’t research quantum mechanics but I was fascinated by the mystery that lies in the foundation of the observable world, of which the most familiar example is the wave/particle duality of light. I thought it was a good metaphor for human personality. The language of espionage lends itself to this duality—think of the double agent.