‘If I knew that my son’s art teacher was banging his brains out in the art room, I’d be in there with a meat cleaver.’ Cate Blanchett is reflecting on her new film, Notes on a Scandal, in which she plays an art teacher who has an affair with one of her pupils. It was, she says, her most challenging role to date.

‘I certainly can’t imagine doing what Sheba did; breaking apart her life in such a spectacularly devastating way. She’s an adult and he’s her student. There’s a responsibility that goes along with being a teacher,’ says Blanchett, who is sitting in her suite in Claridges hotel in London’s Mayfair. ‘It’s really been the hardest journey I’ve ever had with a character, because I look at a 15-year-old boy and all I see is a child.’

Adapted from Zoë Heller’s fact-based novel by playwright-turned-screenwriter (and friend of the actress), Patrick Marber, Notes on a Scandal is set in a north London school. The affair Blanchett’s character has leaves her vulnerable, not only to dismissal from her job and criminal charges, but also to extortion by a lonely and manipulative colleague. While the film focuses on the relationship between the two women - fey art teacher Sheba Hart (played by Blanchett) and her domineering colleague Barbara Covett (a terrier-like Judi Dench) - it is the one between the woman and boy that’s causing a stir.

All of which, Blanchett says, was the main attraction of playing the part. ‘I’m not particularly interested in playing characters that think the way I do,’ she says. ‘I played mothers before I was a parent. And then there’s the old cliché: you don’t have to have murdered someone to play a murderer.

‘But I really liked playing this part, because I’m not living it. I’m not running out of my front door in my pyjamas into the paparazzi every morning. You do go home every night after work and think, “Thank Christ! I’m in a very healthy relationship”.’

In spite of being worlds apart from Sheba (or perhaps because of it), Blanchett has really nailed the character. It’s to her credit, and that of Marber, Heller and the film’s director Richard Eyre, that Sheba’s moral transgression is made understandable, if not either palatable or forgivable. Blanchett’s performance has been recognised with Golden Globe and Oscar nominations.

The past couple of years have been incredibly busy for Blanchett. She is currently in cinemas in the critically-acclaimed Alejandro González Iñárritu film Babel with Gael Garcia Bernal and Brad Pitt and is in the forthcoming Steven Soderbergh film noir The Good German. Other projects in the pipeline include Todd Haynes’ unconventional Bob Dylan biopic I’m Not There and The Golden Age (a sequel to Elizabeth), both of which she has recently finished filming.

Dressed in a short black dress and knee-high boots and wearing her blond hair scrunched and loose on her shoulders, the 37-year-old Australian looks fresh faced and is glowing with health. Her relaxed but engaging demeanour suggests that far from being worn out by work, she is thoroughly enjoying being at the top of her game. Still, Blanchett readily admits, ‘I’ve had an extraordinary couple of years, and I wouldn’t want to replicate a year like the last. It’s an enormous amount of work to do in one year, but then the diversity of roles like those doesn’t come along every year. Nevertheless, I’d be more than happy to do a film every year, or every other year. I mean, I also have two young children.’

She has been nominated for four Golden Globes in the past, for The Aviator, Veronica Guerin, Bandits and Elizabeth, which resulted in a win. The 1998 biopic of Queen Elizabeth I was Blanchett’s fourth film and it brought her international recognition as well as her first Oscar nomination.

While Blanchett maintains that she prefers the stage to film acting, once a career in the latter took off and Hollywood inevitably beckoned, there was less time for her first love. Blanchett moved to London around the time she made Elizabeth, partly because her husband, the Australian scriptwriter Andrew Upton, was working in the UK. The couple were based in London and Brighton until recently, and both of their children, Dashiell John (five) and Roman Robert (two), were born in the UK capital.

She has worked with some of cinema’s top filmmakers and actors, making consistently interesting films that span both arthouse and blockbuster. She landed a plum role in the biggest blockbuster of recent times, The Lord of the Rings trilogy, playing the pointy-eared elf queen, Galadriel. The prosthetic lugs share pride of place in her home with the Oscar statuette she finally received in 2004 for her turn as Katharine Hepburn in Martin Scorsese’s Howard Hughes biopic The Aviator.

‘When the “golden guy” came my way, I thought “It’s a bit of a curse”,’ she says. ‘“The phone’s going to stop ringing now that you’ve arrived somewhere”. Not that you feel you have arrived somewhere yourself, but that you’re perceived to have done so. They [Hollywood] are always looking for the next thing. But fortunately the phone hasn’t stopped ringing. I’ve been very lucky.’

Lucky or not, far from curtailing her career success Blanchett’s Oscar win compounded it. After a brief return to Australia in 2005 to make the gritty drug drama Little Fish, the triumvirate of Babel, The Good German and Notes on a Scandal ensured Blanchett was busier than ever before. At this stage in her career one imagines the actress could have any role she wanted. But, she says, ‘I find it hard to say, “Cast me, cast me”. And audiences tire of seeing the same face on the big screen.’

So in what could be seen as a contrary move, Blanchett has decided to put her film career on the backburner for a while. She is in the middle of filming The Curious Case of Benjamin Button, a romantic oddity with her Babel co-star Brad Pitt, about a man who ages backwards. After that she has no plans to make another film this year. Instead, she and her family are relocating to Australia. She and Upton are to become joint artistic directors of the Sydney Theatre Company, where Blanchett cut her teeth as an actress. In advance of their three-year tenure, the couple directed a double-bill of one act plays for the STC, Upton overseeing Mamet’s Reunion and Blanchett directing Harold Pinter’s A Kind of Alaska.

Blanchett is clearly excited about her new project. ‘We have a five-year-old who will be in school this year, and he’ll need to be in one place,’ she says, ‘so yes, we’ll be in Australia. Australia’s an incredibly vibrant place. And the opportunities the Sydney Theatre Company will afford us both are utterly expansive. There are a lot of latent skills I’ve been developing that will hopefully benefit the company. The fact that my husband is a writer and I’m an actor are major strengths. And we’d love the company to tour as a long-term plan. So I feel quite galvanised by the opportunity.’

As the interview comes to an end, I ask Blanchett if she is the kind of person who responds well to chance. ‘Things present themselves to you,’ she says, ‘and it’s how you choose to deal with them that reveals who you are. We all say a lot of things, don’t we, about who we are and how we think. But in the end it’s your actions, how you respond to circumstance that reveals your character.

‘Also,’ she adds, ‘I don’t understand a way to work other than bold-facedly running towards failure. I think it’s always good to take on things that at first seem bigger than you. Then you just try and surmount them.’

Notes on a Scandal is on general release from Fri 2 Feb.

A star for all seasons

Little Fish, in 2005, scooped her an AFI Best Actress award. As well as Babel and Notes on a Scandal (see opposite) she will soon appear in I’m Not There, The Golden Age, and The Curious Case of Benjamin Button.