Some actors talk the talk, and others walk the walk. William Shatner — well, he does both. Having played Captain James T Kirk, commander of the Starship Enterprise, on television and in film for almost 30 years, it seemed almost too perfect when Sir Richard Branson announced Shatner would be venturing into space after signing up to take a Virgin Galactic flight.

Even at 76, Shatner has lost none of his thirst for action. When I met him on the set of Boston Legal, the Emmy award-winning drama that has belatedly rekindled his small-screen career, he was trying to bunk off filming to go stock car racing.

“I want to get three days off,” he explained conspiratorially. “I want to go drive in a Nascar [National Association for Stock Car Auto Racing] race. I’ve driven in grand prix races, which is enviable enough, and I’ve been trained to drive fast cars. But now Nascar wants me to come and drive in Charlotte, North Carolina, which is the birthplace of the sport. Well, I mean, that’s incredible, right?”

In his spare time, Shatner is quite the petrolhead. “They have celebrity grand prix where you race against other celebrities and pros who start a little further back,” he enthuses. “I do them all the time.

“They require you to take training, so you go for four days to driving school. I’ve done that four or five times and driven 150mph down a back street somewhere and into chicanes and around 90-degree turns, and it’s fantastic.”

Off the racetrack he drives a black BMW X5, and he likes to push it to its limit. “The fastest I’ve ever driven outside of a race?” he ponders. “I’ve probably had a good car up to 120, 130mph. I love cars and I drive fast all the time.

“Basically I’m a fan of machinery. I love everything mechanical — I love watches, cars, I love the machinery of guns. I love our ability as humans to make tools.”

What about speeding tickets? “In this last year I’ve had none,” he smiles. “But I recently purchased a Porsche and they warned me to be really careful because the cops look for Porsches. So I’m actually not straining it and taking every precaution.” He pauses, then adds: “Although when nobody’s around I floor the mother.”

Shatner, who married for the fourth time in 2001, has a 360-acre farm and ranch in Kentucky. When he’s not working or racing stock cars, he likes to relax with a spot of horse riding. But if you’re imagining a gentle canter around the paddock, think again.

“I breed horses and compete in three different events,” he says blithely. “I compete on a horse called the American saddlebred, which is a show horse, and you attempt to show that horse in its beauty and its passion, which involves plenty of speed.

“I also compete in trotting horses with 10 other people in a narrow oval, which can get quite dangerous as the other guy is up close with a 1,500lb horse running at you.”

Isn’t this all a bit much for a septuagenarian? “Out of my eyes, I am seeing the world as a 35-year-old,” he says flatly. “I look in the mirror every so often, and I go, ‘Oh, God, where did that come from?’

“You’re seeing me as an old guy. I don’t think of myself as that. I think of myself as the guy in Montreal or maybe a bit later.”

Shatner was born in Montreal, in the heart of French-speaking Canada, and studied commerce at the city’s McGill University before taking drama classes, starring in various Shakespeare productions and then making his Hollywood movie debut in 1958 in The Brothers Karamazov alongside Yul Brynner — all several years before most people’s enduring image of Shatner in a tight mustard top with slicked-back quiff at the helm of the USS Enterprise.

Such a youthful self image may explain why, in 2002, he arrived at a charity event by parasail — flying through the air attached to a parachute. “What’s not to like?” he laughs. “You put a propeller on your back, with an engine and a parachute sail. You run like hell, yank the throttle and jump into the air. And you fly with the birds. It’s the most incredible experience. To fly!”

So he must be looking forward to the ultimate flight — to the edge of space in a Virgin Galactic shuttle. “No way, are you crazy?” he laughs.

Clearly the reports of him being an eager ambassador for Virgin space flights are a tad wide of the mark. “One little tile burns and you drop to your death? I’ve been approached to do some things with astronauts and the preparation that astronauts go through. One of the things you have to do is get used to weightlessness and they have a Boeing plane that does an outside loop so you’re weightless for about 30 seconds. It’s called the Vomit Comet and I don’t like to vomit.”

The idea seems to depress him and he’s suddenly feeling pensive. He talks briefly about his third wife Nerine Kidd, an alcoholic who drowned in their pool.

This leads to darker thoughts. He does worry, he explains, about oil dependency even though he loves cars so much. “I see a very difficult time coming for the world,” he says. “Clean water and air are becoming rarer. If I could, I’d legislate for more miles per gallon.”

To lift the mood I ask what dreams Shatner still wants to fulfil. “Not to get sick,” he says. “I’m so healthy and I feel so strong and I jump up on a horse and I drive fast cars. And I’m thinking this has got to end soon, and I don’t want it to end. That’s my biggest dream.”

On his CD changer

Ben Folds’salbum Fear of Pop. Ben’s a good friend. He produced and co-wrote on my second studio album, Has Been, in 2004. And I make a sneak appearance as a studio producer in the video for his song Landed

Up Till Now, The Autobiography Buy the book