Acting is anything but easy Previous attempts by members of the Royal Family to "crack Hollywood" have not inspired confidence. Prince Andrew's Forrest Gump 2 met with an unenthusiastic response from the critics when it was released in 1995 ("A true stinker" - New York Times; "I wanted to gouge out my own eyes" - Variety) and the Princess Royal's performance as the bowler-hat-and-suspenders-wearing Sally Bowles in Cabaret: The Sequel is still cited as the third main reason people visit trauma counsellors, after 9/11 and the Indian Ocean tsunami. So what was Diana, Princess of Wales thinking when she allegedly told Kevin Costner in 1996 that she was "interested" in taking on the Whitney Houston role in The Bodyguard 2? Well, assuming Costner's revelations of last week are true, I think I know. She was thinking: this acting business looks like a complete doddle. Because the same thought has crossed the mind of anyone who has ever seen a movie. I suppose the problem is that acting does not seem to require any special skill, in the way that playing a violin or painting a still life in the style of a Flemish master does. Sir Ian McKellen helpfully explained his craft to Ricky Gervais's character in Extras: "How do I act so well? What I do is I pretend to be the person I am portraying in the film or play. It's perfectly simple. But of course it can't be that simple, otherwise we would all be able to earn millions "pretending" in front of the cameras. Just as the X Factor auditions are full of singers who are tone deaf and don't know it, so people delude themselves into thinking they can act, when they are in fact more wooden than a wooden spoon, on a wooden table, in the middle of a wood. My wife and I have a shorthand for when we realise we have tuned in to a bad drama on TV. "Actors," we will say, with a knowing nod. This means you can see the person acting, which rather defeats the object. No wonder some actors are quite prickly about their trade. I once put it to Charles Dance that it was not quite a proper job for a grown man. "Some might think it's a job for children," he said in a loud, indignant voice, "but it's not! We do work very hard. I don't know about that, but it is certainly true that some are better at it than others. Kevin Costner, it has to be said, it a pretty good actor. The greatest, for my money, were Paul Newman and Steve McQueen. When they were on screen you simply couldn't take your eyes off them. And there are some actors who take their business very seriously, such as Laurence Olivier who kept awake for three days during the filming of Marathon Man, because his character was supposed to have been awake for three days. When Larry explained to his co-star Dustin Hoffman why he was so tired, Hoffman said: "Try acting, dear boy, it's much easier." I know, I know. I was just testing you there. Being a method journalist I like to experiment with the form. Like Meryl Streep in The Iron Lady, I'm all about the "total immersion" and the sturm und drang. I'd never really rated her as an actress before that film, never been able to see beyond her overpowering Meryl Streepness. But in that performance she inhabited her character in a way that was supernatural. I forgot it was Meryl Streep within about 30 seconds. And that, I'm afraid, is why not everyone, not even Princess Diana, can be an actor.