Anna Chancellor has a lineage worthy of Tatler but has had to scrap to establish herself as one of our finest actors

Chancellor has come a long way since Four Weddings. The British actor talks motherhood, her new role in Mapp and Lucia, and why she shuns her aristocratic roots

Chancellor says: 'I found my life quite tough to be honest with you' (Clare Hewitt)

Anna Chancellor has taken hold of the print-out of her Wikipedia entry that I have brought along to our interview, and is muttering to herself as she pours over it: "I don't believe it... Who do you think wrote this?... Can I edit it?... God Almighty... I can't bear it." The subject of her horrified incredulity is a section headed 'Family', in which Chancellor's purported lineage is set out in considerable detail by Wikipedia's anonymous genealogist. And although she won't thank me for doing so, it's worth quoting in part.

'Chancellor is the great-granddaughter of Raymond Asquith and the great-great-granddaughter of Prime Minister HH Asquith', it reads, 'and through her father she is the great-granddaughter of the 12th Earl of Winchilsea and Nottingham (a descendant of Thomas Cecil, 1st Earl of Exeter and William Cecil, 1st Baron Burghley). She is a second cousin, once removed of actress Helena Bonham Carter ... Her uncle is journalist Alexander Chancellor … her six-times great-aunt was author Jane Austen. She is also 10 times a descendant of Mary Boleyn, twice of Richard Rich and once of John Churchill, 1st Duke of Marlborough.' And so it goes on.

"I've never looked at it because I'm so embarrassed by it and now I'm looking at it," she says. "God Almighty... [no, He's not listed in her Wikipedia entry]. Can't you imagine? You've worked hard all your life to be an actress, or whatever you've done, and that is what's presented to you. Don't you think that's embarrassing? I don't enjoy being quoted as saying that's who I am, because I don't feel that is who I am."

One woman who wouldn't be embarrassed by such a noble lineage, in fact who would positively delight in showing off about it, would be Emmeline 'Lucia' Lucas, queen bee of small-town society in the 1930s and heroine of Edwardian author EF Benson's Mapp and Lucia comic novels. The League of Gentlemen's Steve Pemberton has re-made some of Benson's stories for television, and they are one of the main planks of this Christmas's BBC schedule. Miranda Richardson plays Elizabeth Mapp, Lucia's rival for social prestige in the fictional seaside town of Tilling (based on Rye in East Sussex), while Chancellor plays Lucia. "She's horrible isn't she?" says Chancellor. "Lucia is appalling – she's dominating, she's a snob, she's a phony... she's hilarious."

Did she read Benson's novels as research? "I read a couple. To be honest, I found them a bit boring ... I was also reading Isadora Duncan's life story which was so mad and compelling that I had to force myself to pick up EF Benson."

Chancellor (right) in the BBC's 'Mapp and Lucia' (BBC)

That's a thing I like about Chancellor; you don't get any PR puff, and for one moment I thought she was going to write off the whole project. "But when I saw it acted, I was so taken up with how clever everyone was... how you'd have a whole episode about whether Lucia had pretended to do a drawing or not, and you might think, why would anybody care? But strangely it did seem to matter when you were doing it and I became completely immersed in it. Luckily, because I was in it...

"I suppose that's what I'm saying, is that I wouldn't really be bothered," she says of Mapp and Lucia's social one-upmanship, or one-upwomanship. "I've probably spend a lot of my life disentangling myself from that kind of thing, because it's just not what interests me."

What interests her, it turns out, are bluegrass music (she's off to a bluegrass festival in Arizona shortly after we meet), documentaries and "the more obscure, handmade things in life... full-on popular culture doesn't really interest me."

To use an old-fashioned term, you might call Chancellor déclassé; for as she once said: "I came from a wealthy family but I had no money... it makes it worse because you have a sense of entitlement". It might be more accurate to say that she is a fully paid-up member of the great Metropolitan melting pot, living in Acton in west London with her second husband, Redha Debbah, a first-generation Algerian immigrant whom she met when he taxied her back and forth from a West End play 17 years ago.

Anna Chancellor and Miranda Richardson in Mapp And Lucia (BBC) ((C) BBC - Photographer: Nick Briggs)

She was a single mother in her early twenties (more of which later), claiming to have never passed an examination in her life ("I just didn't fit into the education system at all") and "for ages it didn't look like I was ever going to get a job," she says. "I found my life quite tough to be honest with you. I experienced a lot of things and now I'm nearly 50 I think I have a lot of things to draw on. That's why I get annoyed by that [Wikipedia], if you think that's the sum-total of Anna."

Her father, John, was a rare-book dealer in Kew. Her parents divorced when she was two, her mother, Mary, marrying her father's best friend and taking the four Chancellor children to live with them (plus two step-siblings and a half-sister) in an old rectory in deepest Somerset. Sent to boarding school at seven, convent at 11 (cue Chancellor breaking into song: a snatch of Frank Zappa's "Catholic Girls"), Chancellor arrived back in London as a clueless, somewhat disorientated 16-year-old.

"I was supposed to be doing my A-levels but I didn't really do that," she says. "I lived with my great aunt and uncle in Holland Park Avenue, and I was meant to be at college, but it was massive. I had come from a convent and suddenly I was in a college with 5,000 people and I didn't know how to fit in or even listen. Eventually my mother realised I was literally roaming around London."

Chancellor and Hugh Grant in 'Four Weddings and a Funeral'

Roaming around London with quite a fast set, it seems, including a young Peruvian photographer called Mario Testino, Keith Allen and the Pogues' Shane MacGowan, a good friend of Chancellor's then-boyfriend, the poet Jock Scott, who is the father of her daughter Poppy.

"It was quite funny, our relationship," says Chancellor of Poppy, now an artist and illustrator in her twenties. Apparently, Poppy would occasionally find her mother lying on her bed pretending to be dead. "Yes, that wasn't a very funny joke to play on a child. Poppy said it was awful. I remember we used to sleep in the same bed for years and she used to say to me in the middle of the night, > 'Mum, have you turned into a lizard?'. It was the idea that when the lights are out and everything's dark, do you know who you're next to? But it probably had more meaning than that – that she didn't really trust who I was."

There were tough times as a largely unemployed actor (Chancellor had by this stage graduated from drama school, but was eking out a living as a life model) and single mother in Shepherd's Bush, before Shepherd's Bush became even remotely desirable. But Chancellor sees it otherwise: "To have had Poppy so young... I can't even tell you how lucky I am," she says. "You think times are rough sometimes and yet things work out."

Things worked out for Chancellor when in 1994, aged 28, she was cast as the hapless Henrietta in Four Weddings and a Funeral. Encouraged to audition by a friend who said, "It's about posh people fucking in the back of Land Rovers," Chancellor apparently stood out thanks to her shoes, a pair of kinky black Manolo Blahniks that were admired by director Mike Newell.

Anna Chancellor and Toby Stephens in 'Private Lives' at London's Guilgud Theatre (Rex Features)

It was Four Weddings that gave Chancellor the unflattering nickname by which most punters (as she calls the general public) still know her today. "So, Duckface, yuh," she says. "It would be churlish to mind – and you can't mind something that you can't change – and it's much worse in other languages. In Italian it's 'arsehole face' and in Hungarian it's 'horse-cheek face'. The irony is that I love ducks. I had a pet duck... I adored her. I found it in Shepherd's Bush, in the back of a garden, these gypsy guys had this duck and I rescued it." As you do.

"You can't take the image of yourself too seriously because you endlessly get deflated," she goes on. "It's like this auction at a charity [The Arthritis Society] where I'm the patron and in front of 400 people they auctioned me off to have lunch with and no one bid except my daughter and a friend of mine who thought they'd get the bidding going, and my daughter ended up winning... £600 to have lunch with her mother." To add insult to injury, a signed autograph of Tony Blair went for thousands.

Until Four Weddings and a Funeral, Chancellor's main claim to fame had been a sci-fi soap opera, Jupiter Moon, in which she played a character called Mercedes Page. "I've had some brilliant character names over the years," she says. "I was called Questulor Rontok [in The Hitchhiker's Guide to the Galaxy], Hope Goodgirl [A Touch of Cloth], Carmen Svennipeg [Staggered] and Lix Storm in The Hour."

In the 1995 BBC adaptation of Pride & Prejudice – the one with Colin Firth as Mr Darcy – she played Caroline Bingley, another woman spurned. "Being a spurned woman – it wasn't something that I had particularly experienced in my own life," she says in a matter-of-fact rather than a defensive or show-offy manner. "I wasn't somebody who men ran a million miles away from when I was younger. I had quite a few boyfriends."

Chancellor was married to the cinematographer Nigel Willoughby for six years in the 1990s, before meeting Redha Debbah – a rare example of matchmaking by a cab operator. "She said I might quite like him," says Chancellor. "I remember saying that to Colin Firth and he said, 'Oh my God, are you telling me there are rivals everywhere, in every cab, we've got to look out for them everywhere? He suddenly looked very exhausted."

Chancellor starred opposite John Thaw in hit show Kavanagh QC in 1997 (Rex Features)

Attractive to men, but not to casting directors in search of romantic leads, it would seem. "Maybe I seem too combative." There is an upside to this, of course, with more interesting roles and greater longevity. Since the Fifties-set newsroom drama The Hour, a show she thinks that the BBC was premature in axing, Chancellor's career seems to have been reinvigorated. There was a well-regarded West End run in Noël Coward's Private Lives, roles in two of the more interesting TV shows of 2014, Inside No 9 (Steve Pemberton again) and Penny Dreadful, a guest slot as a servant-bedding aristo in Downton Abbey and now Mapp and Lucia. Was there – post Four Weddings perhaps – a time when Hollywood came calling?

"Not... at... all... literally, not at all," she repeats. "About 10 years ago I went with Redha to see if I could get a job in Los Angeles and I'd had my hair done and spent all this money on trying to look good and the American guy interviewing me went, 'Oh my God, you English girls are so great but you just don't care what you look like'...

"But who knows? Maybe if I had been someone else... a different character... different timing... but actually it all worked out quite well. It was better that I stayed in England; I am probably very English." Chancellor is also good company, which always helps during filming with its long bouts of waiting around. "I think my key attribute was that I was always open-minded and always interested, even when it looked like everything was going very bad, I don't think I got bitter. I was always up for life, interested in other people, interested for new experiences. Somehow people want you on board".

'Mapp and Lucia' begins on BBC1 on 29 December at 9.05pm