Helena Bonham Carter: In all the best circles

It's been quite a couple of weeks for Helena Bonham Carter: major roles on the BBC over Christmas; the release in the cinema of the much lauded The King's Speech, in which she plays Queen Elizabeth to Colin Firth's stammering George VI; and then, in real life, perhaps the most eye-catching appearance of all, out enjoying a New Year's Day walk in the Chiltern hills with, among others, the Prime Minister and his wife.

Bonham Carter, who is friends with Samantha Cameron, had been a guest at nearby Chequers with her husband, the film director Tim Burton. The snap taken by the walker who chanced upon their group, which also included the Education Secretary, Michael Gove, was revealing about the nexus of politics and showbiz that is such a feature of public life but which is rarely glimpsed so informally.

One guesses that Bonham Carter's great-uncle, the film-maker Anthony "Puffin" Asquith, wouldn't have been altogether delighted to see Helena in such company. Asquith – director of The Browning Version and The Winslow Boy – was a fervent trade union man: he served as president of the film technicians' union ACT for more than 30 years. Then again, Bonham Carter's wider family – distinguished in a variety of fields – has a strong connection with 10 Downing Street. She is the great-granddaughter of former Liberal prime minister Herbert Asquith (nicknamed "Squiffy" because of his drinking exploits).

At 44, Bonham Carter the actress has not quite yet acquired national treasure status, but her latest performances might well have helped her along the way. In Toast, the adaptation of the memoir by food writer Nigel Slater, she was almost unrecognisable as Mrs Potter, the cleaner from Wolverhampton with the divine touch in the kitchen. She did not altogether sacrifice her usual kooky glamour, but chain-smoking home helps discussing the merits of rival cleaning products are less her stock in trade than ethereal English-rose types or mad Gothic queens and witches.

A few days later, the Beeb re-screened Enid, the biopic of children's writer Enid Blyton that netted Bonham Carter an Emmy for her performance in the title role. And while The King's Speech features one of her less showy performances, she has been winning plenty of plaudits for it. As Bertie's caring, devoted and rather haughty wife, she is the one who goes incognito to the offices of Lionel Logue (Geoffrey Rush), the Australian speech therapist who takes her husband on as a patient. Bonham Carter is decked out in an array of furs, hats and gloves and looks a convincing enough match to the young Elizabeth Bowes-Lyon.

This flurry of exposure will only increase her fascination to media and audiences alike. Her relationship with Tim Burton and their living arrangements are pored over endlessly. They live in adjoining properties in Hampstead. Why? He snores; she's bossy. Bonham Carter is clearly exasperated that much of the British press seems to regard her as an extension of some of the more outlandish characters she has played in Burton movies. "They say Tim and I are a mad couple with subterranean tunnels between our adjoining houses, and that our children live down the road with another couple," she recently told the Radio Times. "We just have two houses knocked together because mine was too small. We see as much of each other as any couple, but our relationship is enhanced by knowing we have our personal space to retreat to."

Whether it's Elsa Lanchester or Joyce Grenfell or Margaret Rutherford, the British love their eccentrics. Part of Bonham Carter's appeal is surely that she is so different from conventional British celebrities. That may to do with the fact that her north London upbringing was not without its challenges – her mother had a nervous breakdown when Helena was only three and subsequently retrained as a psychotherapist.

Bonham Carter has an air of glamour about her but she does seem mildly dotty in a Rocky Horror Show sort of way. What is also apparent is that she is thriving as an actress at an age when many other female stars find the roles disappearing. It helps that she is now equally adept at leading roles and character parts.

Bonham Carter's career has confounded critics who, in the mid-1980s, were wont to dismiss her merely as the "Queen of Corsets". They had seen the Golders Green-born actress as the prim Miss Lucy Honeychurch, "the young English girl transfigured by Italy", in Merchant-Ivory's film version of E M Forster's novel A Room with a View (1985) and as the ill-fated young queen in Trevor Nunn's Lady Jane (1986). There was a danger that she would never escape from the world of handsomely crafted British costume dramas about fey, well-spoken English women.

Even when consigned to this cloistered hinterland of British heritage cinema, Bonham Carter gave some formidable performances. She was affecting and unsettling as the mad Ophelia in Franco Zeffirelli's Hamlet (1990) and showed a steely edge as the ruthless, upwardly mobile woman out to net a fortune in Iain Softley's adaptation of Henry James's The Wings of the Dove (1998). In a perceptive review, The New York Times likened her in this role to "a witchy, English Scarlett O'Hara, whose impatient, sulky glances steadily deepen into a brooding, hunted expression as she becomes aware of her own corruption".

The mischief and subversive quality in Bonham Carter were given free rein in David Fincher's Fight Club (1999) in which she played Maria Singer, a punkish, blue-collar femme fatale with a filthy mouth. Her frantic sex scenes in seedy apartments with Brad Pitt helped to exorcise memories of all those well-spoken frock films and literary adaptations. "She has the ability, very rare in an actress, of being able to play virgins convincingly, which has given her a sinecure in costume parts," Lynn Barber said in a barbed compliment. Post-Fight Club, she was regarded in a very different light.

There has been almost a recklessness about the way she has managed her career. Other British actresses from her background might have baulked at roles like Maria Singer or passed on the chance to portray a sad-eyed monkey (as she did in Burton's Planet of the Apes) or avoided playing a wheelchair-bound character with motor neurone disease who wants to have sex, as she did in Paul Greengrass's The Theory of Flight (1996). Bonham Carter, whose own father suffered a stroke that left him wheelchair-bound, blithely threw herself into such roles.

The relationship with Tim Burton underlined her gothic credentials. If casting agents were looking for Morticia Addams types, she was one of the first names on the list: witness her performance as Bellatrix Lestrange in Harry Potter. Meanwhile, she is still in demand to play queens, whether her petulant and temperamental Red Queen in Burton's Alice in Wonderland or her much more restrained turn as Elizabeth in The King's Speech.

Unlike the Maggie Smiths, Judi Denches and Helen Mirrens, Bonham Carter doesn't have a glittering stage career to set alongside her film work – so she is unlikely to be made a dame quite yet even if she does consort with prime ministers and their wives. However, as she recently acknowledged, "Ageing has been good for my career." In the 1980s, she was regarded as upscale British cinema's ingénue of choice – and not much more. Twenty years on, she is far harder to pigeonhole. An actress once typecast in a very narrow range of roles now seems capable of anything. She can play a cleaner or a queen without anyone questioning her right and ability to do so.

A life in brief

Born: 26 May 1966, north London.

Family: Her father was a merchant banker and her mother a psychotherapist. The youngest of three children, she is the great-granddaughter of the former prime minister Herbert Asquith. She is married to the film director Tim Burton, with whom she has two children, Billy Ray and Nell.

Education: South Hampstead girls' school.

Career: Acted in commercials as a teenager. Film breakthrough came in 1985, in her second film, A Room With a View. Nominated for an Oscar in 1998 for The Wings of the Dove. Other films include Fight Club, four of the Harry Potter films and The King's Speech. Has acted in six films directed by her husband, including Alice in Wonderland.

She says: "Usually I'm frustrated when I look at my films and I don't believe that I've made a real transformation beyond my usual sets of gestures."

They say: "I don't know you but you were the first person I thought of to play a chimpanzee." Tim Burton's first conversation with her