The thick mop of tousled hair is instantly familiar, So too is the
strong face, the determined jaw and cheekbones, not to mention the dark, impenetrable eyes. And then there's the voice. It has to be Mr Darcy - the man who emerged dripping from a lake, bare-chested, wet breeches stretched taut, in Pride And Prejudice.

But on closer inspection there are subtle differences. This is not
Colin Firth but his younger, equally transfixing brother, Jonathan. At 30 years old, and relaxing in black leather jacket and jeans, Jonathan looks as though he could do a pretty good job of that lake scene himself -while attracting the same army of adoring female fans. And that's exactly what may happen when he's seen playing the dashing and dastardly Sergeant Troy, complete with scarlet military tunic and gold braid, sword at the side of his crisp navy breeches, in ITV's dramatisation of Thomas Hardy's Far From The Madding Crowd, which begins tomorrow night.

It's his seduction of Bathsheba, the beautiful, proud and wilful
heroine, that is most likely to get the women hot under the collar. "He uses his sword to demonstrate his prowess - he offers to show off his drill. Having told her that the sword isn't sharp, he sweeps it around her face in a blur of steel, and then finally takes a piece of her hair and slices it off with the blade. It's as sharp as a razor," Jonathan says with a glint. "Of course, she is utterly smitten - what woman wouldn't be? It's a lot more stylish than coming over and asking if you can buy her a pint!" And so begins a relationship that can only end, like so many in the novel, in utter heartbreak.

The film version of Far From The Madding Crowd transformed the careers of its stars. Julie Christie, who played Bathsheba, became an international celebrity; Alan Bates was the surly Gabriel Oak; Peter Finch portrayed Boldwood, while Terence Stamp took the part of the infamous Sergeant Troy. Each role was to have a profound effect on their lives. Should the same happen to Jonathan, it will come as something of a relief. It means he will finally be able to step out from the shadow cast by his brother. He will no longer be Mr Darcy Junior.

"Although people now that professionally I've been around for a long time, there is also this presumption that I' ve been riding on Colin's coat-tails," he says. "There's this notion that I must have thought it all looks rather easy and I'll have a piece of it. "I'm not sure whether Colin's success has been helpful to me or a disadvantage. There's the notion that they can get Mr Darcy, or something like him, but at a cheaper rate. But you could also argue that if they want Colin then they go after him, so why would they want me? In the end I have to pursue my own path."

Jonathan's desire to act came not from his brother, but from performing in a local comprehensive school production at the age of 11. "It was the most exciting thing I'd ever done," he says. "I was hopeless at sport, but this was something I was really good at." Colin was seven years older than him, so the gap was too great for any sibling rivalry. "1t's only as we've got older that we've become closer," he says. He didn't act again until he went to sixth-form college, and by then he was desperate to perform. "I never wanted to be anything else," he says. For his academic parents, it must have been their worst nightmare.

His father was a lecturer in American History at Winchester College of Higher Education, while his mother lectured in psychology at Surrey University. Yet all Colin, Jonathan and sister Kate, now 34 and working as a voice teacher, wanted to do was act. "They were bewildered by the fact that none of their children wanted an academic career," says Jonathan. "It was Colin's fault - he started it. He went to drama school, not as a career, but for something to do. After that we became actors by default.
"But in getting work and making a success of things, Colin demonstrated to my parents that it could be done, and that made it easier for me to persuade them. But even if he had been a disaster it wouldn't have put me off. "The fact is that I had very few expectations anyway, I saw going to drama school as a way of continuing something I enjoyed, but I had no ambitions beyond doing some rep and being a spear carrier." But now success stares him in the face - and the prospect makes him shudder.

"I wouldn't want the attention Colin had with Pride And Prejudice, with people following him into restaurants," he says. "I've seen the price of success and I really don't want that."

Jonathan is currently filming An Ideal Husband, with Prunella Scales and Robert Hardy. For the millions of women who will soon be swooning over him as Sgt Troy, there is hope: while Colin is an ideal husband in real life, his swashbuckling brother is most definitely still single...

Thanks to Maria