Yet it's not a case of all talk and no action. After first working together on 1999's improvised docu-fiction The Protagonists, they began discussions about 'a kind of cinematic atmosphere', as Swinton puts it, that they wanted to create.

Eleven years later, the result is I Am Love.

Visually lush and sonically rich - thanks to an operatic score by John Adams - the story began to brew after Swinton made Guadagnino's 2002 short, The Love Factory, a one-take close-up of her speaking about love. She plays Emma, a Russian emigre married into a wealthy Italian clan, in I Am Love.

'I had this idea of this woman living in this house,' Guadagnino says. 'What does she feel? What does she think? What does she want to do? Tilda and I then spoke about this idea of classical cinema becoming modern again. And she immediately connected with that.'

An intelligent, searing study of infidelity, betrayal and love, I Am Love has already been compared to the masterworks of Italian cinema - in particular the films of Luchino Visconti. Guadagnino is cautious about such praise. 'We wanted to be modern as Visconti was when he did his movies. We didn't see Visconti as a master of the museum of cinema. That's what we wanted to do: to be Visconti when he was 40 years old, not Visconti when he was dead.'

Swinton - acting in Italian, though speaking in Russian throughout - concurs, noting that the world of I Am Love is very different to that of, say, Visconti's The Leopard or Rocco and His Brothers. 'We started to think about the milieu of the bourgeoisie - particularly Milanese society, which is very particular. It's not often looked at. This is not the feudal aristocracy of Visconti, which has a different code and history and is much, much older. This is a relatively recent phenomenon. This is 'Capitalism - the Fairy Story!''

As Guadagnino puts it, modern-day Milan is a secretive place. 'You don't spot the beauty of that town when you first go there,' he says. 'You see just the bad weather and the greyness of the walls. And it's very anonymous. But then if you look closer, you see in this grey facade a lot of details. And then behind these walls, there are these incredibly beautiful and rich houses.

'Power in Milan hides itself. The discreetness of power makes the power last longer.'

While Guadagnino confesses he also watched films by Jean Renoir, Roberto Rossellini and Alfred Hitchcock, a surprising admission is how much of an influence Jonathan Demme is on the film. The title I Am Love comes from a scene in Demme's Philadelphia (glimpsed in Guadagnino's film) in which Tom Hanks translates an aria sung by Maria Callas.

'Jonathan Demme is really one of the greatest filmmakers alive. Greater than many. For example, [he has] a career that is far more exciting and challenging than Martin Scorsese lately ... he's a very inspiring director, and very humanistic. And I like the idea of doing a humanistic film.'

Indeed, as much as I Am Love is an insightful peek into a hermetically sealed social universe, with its complex depiction of Italian family life, it's first and foremost a story about a woman who reaches a crisis point.

Emma, married to textiles magnate Tancredi Recchi (Pippo Delbono) and a mother of three, is beginning to feel surplus to requirements. 'The life of the mother, of growing children, is at an end now,' says Swinton. 'They're beginning to leave and have their own adventures in life and love. Things start to bubble up in her.'

What follows is a traumatic affair that begins after Emma is introduced to a chef named Antonio (Edoardo Gabbriellini). It's the result, says Swinton, of being a woman 'who has lived undercover for 25 years, not even with her own name', which may explain why Guadagnino took his costume designer and cinematographer into Milan to match the drab city walls to the fabric of Emma's outfits. 'We wanted to have a place where Emma can camouflage herself,' the director explains. 'When she walks in the street, she is grey as the walls.'

For Swinton, compared to her Hollywood work (even Michael Clayton, which won her an Oscar), she believes a film like I Am Love is 'my meat and potatoes ... it's the cinema I want to see'. It's why, as an actress-producer, she's happy to spend so much time on it.

'These are films I am growing from seed. If we're talking about things like I Am Love, or the work I make with Lynn Hershman [the uncompromising Conceiving Ada, Teknolust and Strange Culture], it's what I want to see. It's what I'm interested in seeing. Yes, it may take time to grow,' Swinton says. 'But life's too short not to go for what you're interested in.'

It's why she and Guadagnino have formed their own production company, named The Love Factory after their 2002 short. Swinton calls I Am Love 'the first of a series of films we're making', and admits that one of their projects is a remake of Morton DaCosta's 1958 film Auntie Mame. It would certainly be a remarkable role for Swinton. The original starred Rosalind Russell as a flamboyant and free-spirited socialite who is forced to look after her nephew after his father dies. 'She's so perfect for that, no?' says Guadagnino. 'She is Auntie Mame.'

Here's hoping it doesn't take another 11 years before we see it.

I Am Love opens on Oct 7