Brenda Blethyn specializes in playing monstrous mothers, and she outdoes herself in Introducing the Dwights as Jeannie Dwight, an aging, British-born comedian who has to have the last laugh on everyone around her. Clearly, the multiple Oscar nominee isn't afraid to play complicated–not to mention a bit unlikable.

"No, not at all," she says, calling from an office in Toronto. "I'm nothing like Jean, I'm glad to say. But it is a lot of fun to play these women. It would be so easy, you know, to smooth off the edges, to make her more palatable. But that would be patronizing to her, and to you as the viewer. And anyway, it's so boring to see likable people all the time. Isn't it far more interesting to watch the ones we don't like and see if we can change our minds about them?"

The veteran performer, best known for her star-making lead in Mike Leigh's Secrets & Lies, insists that it's important to remember that her new character is at a crossroads, having raised two boys on her own and now about to lose them to adult distractions.

"She's never been like this before," she says of Jeannie's erratic and clearly jealous behaviour, triggered by son Tim (Khan Chittenden) entering into his first real relationship, with precocious Jill, played by impressive newcomer Emma Booth. "We all behave badly at some point in our lives, and she certainly acts inappropriately, with all that screaming and crying."

Blethyn says the script for the film, called Clubland in its native Australia, was written about 12 years ago, when writer Keith Thompson set out to document his relationship with his own mother, a musician on the down-market circuit depicted in the story, and an older brother with a mild case of cerebral palsy.

"He couldn't understand why his mother was so possessive until he had a child, and then it all fell into place. Also, he was fascinated by the world that he was part of back then. When I first read the script, about five years ago, I was struck by how honest the writing was. I thought, 'This has got to be from his own experience.' Especially the stuff about discovering sex for the first time. It was just so refreshing."

The veteran actor realized that her job was not just to find out how far the wounded mother bear would go but to figure out what she was like before she got cornered.

"I mean, she was always a bit noisy. Like Joan Rivers, Jean can't open her mouth without cracking a joke. But this is a coming-of-age for her, not just for her sons, and it frightens her. You might think that she's an alcoholic, but she can't even afford to drink–especially when she has to keep three jobs together. How could she work at the canteen at five in the morning if she drank all the time? So you are meeting them at a crisis point."

What the audience grasps, and Jeannie doesn't, is that Tim has found a good 'un. But with mum's repeated references to "Samantha all over again" and, even more cryptically, "the Seaworld episode", there may be some reason to have worries.

"I don't think there's a mother anywhere in the world who wants her son to give his heart–hook, line, and sinker–to the first girl who comes along, no matter who she is. Anyway, she wants him to stick around for a while longer and have his fun, if you know what I mean."

To this, she adds her infectious, and possibly patented, Brenda Blethyn cackle. But she turns more maternal while talking about her young supporting actors.

"Aren't they fantastic? I am so proud of them, all of them. They were just such a joy to work with. When I read the script, I realized I cared about all these people. There's not a superfluous character there! And then to work with such wonderful young people–well, I just hope it comes across on-screen what a good time we had."

If anything, trailers for the film emphasize the farcical elements too much, skipping over the more tender (not to mention frankly sexual) parts.

"Well, whatever gets them in, eh? Once the audience is there, though, I think they get a more fully rounded experience."

Certainly, Blethyn's track record runs the gamut of emotions. She first got noticed in Leigh's dark BBC comedies, like Grown-Ups, back in the 1980s. And, naturally, she has done plenty of stage work since then (with lots of Shakespeare in the mix), really kick-starting her film career with that Oscar-nominated turn in Secrets in 1996, when she had already turned 50. She has appeared in a stunning 35 projects since then, resulting in more Oscar and BAFTA nominations for her roles in Little Voice and Pride & Prejudice. More recently, there was an eight-hour Euro version of War and Peace, shot in Russia with an international cast.

"It's all completely dubbed, as only the Italians can do it," she explains.

Yeah, but was it possible to dub that laugh?