You've trodden the boards since your teens - but how long have you been pounding a treadmill?
I didn't get serious about fitness training until my early thirties. In my teens, and through drama school at RADA, I played soccer. That kept me sprightly, as did endless dance and movement classes. And in one's roaring twenties the engine simply fires in a different way.

Did you feel you were on a slippery slope in your thirties?
Isn't that the decade when you put the spare tyre on, or is that the forties? Whichever, I just thought, I'm not playing football any more so must take preventive measures on behalf of the waistline.

How did you find a personal trainer?
I was filming Frankenstein (1994) and had to get very fit for the role. I was lucky enough to meet Josh Salzmann, one of America's best-known personal trainers. He trained me for the film and has done so, on and off, ever since. One of the advantages of acting is that you're occasionally required to get into the sort of shape that you'd otherwise never be in. That is, if you want to carry around one less chin than normal. I find vanity a terrific motivator.

So do you want a six-pack like Brad Pitt?
Oh boy, yes. Didn't you think Brad was rather like an anatomical specimen in Troy? His physique gives the impression that it is covered only by a very thin layer of skin. You could imagine it being used in classes to illustrate perfect muscle definition. But I've neither pushed my body that far; nor could it cope with the trauma.

Do you dread the gym like the rest of us?
I used to find working out very difficult. But Josh is talented at taking the dread out of the build-up to a workout. He has instilled in me the idea of an ongoing daily fitness effort. And I've even come to quite enjoy the gym.

Don't you get bored on the hamster wheel?
I am pretty creative about occupying myself during my half-hour on the treadmill, or on the ghastly step machine. I read or listen to music but the telly drives me bananas. Once, while I was reading a script, I became so absorbed I fell off. It wasn't very dignified.

Are you a gym lark or an owl?
For me it has always been a first-thing-in-the- morning thing. I find it energising. Of course, after a heavy night it can be a bit of a bind. God knows I have had periods of falling off the fitness wagon, but if your body is practised it's not too hard to jump back on again.

It's Josh who gets you back on track: is he a Falstaff to your Henry?
Not really, as he's not fat but incredibly lean. But he was very large as a child; something like 10 stone (63.5kg) at the age of 6, which I suppose might be considered Falstaffian.

Is he your mentor?
Josh is a great fitness mentor. He's a Falstaff in that sense. It's good to have someone who is encouraging without being a soft touch.

Are you a calorie counter?
Christ no, life's definitely too short for that. Eat! Eat! Eat! As one gets older the idea of all things in some sort of moderation seems to make a semblance of sense. But that's probably from feeling less able to deal with hangovers.

What's your poison?
Cigarettes. I'm battling with them, with Josh's help, and I hope that this year I'll win. It's not quite a resolution, more a strong intent.

How do you have fun?
One of the larkiest moments I recall, and it was a really terrific adrenalin rush too, was at the end of a very fine but intense and depressing piece of work called Conspiracy. It is about the Holocaust and, at the end of filming we played a football match against the German crew, recreating the 1966 World Cup Final. We won a game played in great spirit 7-2, a great physical release after a difficult job.

So, for you, nothing beats that sporting high?
I am always thrilled and moved by sport. As Matthew Pinsent was weeping away on that Olympic podium, I was blubbing with him. I imagined all those mornings in the cold for a once-in-a-lifetime moment; all that physical effort which most of us abandon after three minutes; the pressure of a world audience and the very fine competitors ranged against you; and finally the theatre of going through it. You saw that most dramatically with Kelly Holmes and Paula Radcliffe - it encapsulated all the agony and ecstasy of sport.

Do you have any plans to bring Shakespeare back to the silver screen?
I hope to direct a film of As You Like It sooner rather than later. It's not absolutely definite but I have grounds for cautious optimism. It's such a treat bringing Shakespeare to the screen and taking advantage of the different possibilities that it offers to the stage.

Do you ever get stage fright?
There are always nerves but I have a routine which involves getting to the theatre early, sometimes ridiculously so. A healthy dose of fear, or apprehension, is all part of the preparation. Before the curtain rises, of course, the tummy flutters. Acting will never be casual for me; walking out live in front of 1,000 people and pretending to be somebody you're not isn't a natural thing for a grown man to do.

But you must have found yourself in some interesting situations.
I was introduced to the world of moisturising on an ice floe in the middle of an Arctic winter. I was shooting a film on the explorer Sir Ernest Shackleton and the temperature was so low that my lips became welded together. The experience made me realise the value of lip balm.