When indie actress Tilda Swinton walked down the red carpet at the Bafta's with 29-year-old artist Sandro Kopp at her side, the immediate consensus was that her long-term partner and father of her twins Xavier and Honor, artist John Byrne (69) had been given the heave-ho.

But when Swinton, the 11-year-old twins and Kopp arrived home to her Scottish pile in the seaside town of Nairn after the ceremony and Byrne greeted them at the door, the public were left wondering just what kind of bizarre love triangle was at work. Who, we wondered, was playing Tilda Swinton's leading man?

Was the 48-year-old actress still in love with the elderly and eccentric Byrne, her partner of more than 20 years who, with his shock of white beard, could pass for her father; or had her affections been given over to her German toyboy, the raffish Kopp, a man who fulfills all the criterion in the old cliche of 'tall, dark and handsome' (and who could easily pass for her son)?

Or was she, as we all hoped in the name of good, honest scandal, sleeping with both of them? Could she -- quelle horreur -- be enjoying a menage a trois with her elderly partner and her toyboy, making her, as one journalist put it, "the luckiest woman in the world"?

Looking at Tilda Swinton, you wouldn't really put it past her. With her flame-red hair, ethereal-looking alabaster skin and 5' 11'' frame, she isn't a woman who aspires to the traditional. She's even referred to her personal style as a "kind of transvestism".

Her body of work has been equally genre-bending, with roles in experimental films such as Orlando, in which she played both the male and female lead, and Julia in which she plays an alcoholic who kidnaps a millionaire's grandson. Even her turns in mainstream productions have steered away from the conventional -- witness her unsettlingly chilling portrayal of the White Witch in The Chronicles of Narnia.

For a woman whose career is regarded for being so very outre, it's difficult to imagine her domestic life being anything less. Hers is a love triangle that leaves the outsider conjuring up images of three liberated artistes, abandoning all convention as they run around a rural Scottish retreat throwing off their clothes and reciting the essays of Bertrand Russell.

But Swinton is quick to dispel any notions of free love and high Bohemia. In fact, according to the actress, her domestic life is "really very dull".

"There has been this idea given out that we're in this complete debauch in this house. Well, that is a fabulous fantasy. It really is very straightforward. You're talking about a couple having children, becoming not a couple any more but remaining the parents of children, and having other coupledoms with other people. It's about consecutive relationships not concurrent relationships. We're not all sleeping together, I'm sorry to tell you. It's so much more boring than that."

sweethearts

The turning point came eight years ago when Byrne, then in his early sixties, grew tired of the peripatetic nature of her work. He decided he would remain in their home in Scotland while Swinton pursued her acting career

"So we agreed that I would go by myself, either with the children or without them. And God it was lonely. It really was. So it was an amazing stroke of luck to meet this fellow traveller."

"Very, very often, people have children with people they are no longer sweethearts with... and then they have a relationship with someone new, right? What rarely happens is that they are still completely good friends and continue to live in the same house. But that's all it is," she argues.

In another intriguing twist to the tale, it turns out that Byrne also has a girlfriend, theatrical lighting designer Jeanine Davies (42). "It's all very relaxed and very amicable," he says "we have not hidden away and Jeanine is very much part of my life."

It all sounds curiously peachy, but then again, euphemisms have that effect. When "our relationship is over" is voiced as "I'm not coming on the road any more" and a "toyboy lover" is described as a "fellow traveller", well, it gives the feeling that discussing certain aspects of this relationship is off-guards, even to those at the centre of it.

When it comes to the technicalities, and the issues such as whether Swinton continues to sleep with Byrne, or whether Byrne has ever been jealous of her toyboy lover, the pair will not divulge. One wonders was she ever involved in an affair with Kopp, or was her decision to find herself a new lover pre-discussed with Byrne? Or if Kopp is to accept Byrne as part of his life, can he also have another woman in his?

And what about the children, how do they feel about the unconventional family unit? "This has been the case for the children for at least half their lives," Swinton reasons.

Swinton is an actress who has relentlessly wrangled with convention. It's not surprising then that her domestic life would be any different. But what's really remarkable is the apparent normality of the arrangement.

Actually, it's pretty staid when compared to most other Hollywood relationship patterns, which are hallmarked by lightning flash courtships and multiple divorces. Swinton, by comparison, spends her time in Scotland baking cakes, growing vegetables and generally living the rural idyll.

For an actress who is renowned for her boundary-breaking work, could her domestic arrangement -- however unconventional -- be where she finds her structure and normality? Or maybe she's just the luckiest woman in the world...

- Katie Byrne