It's a curious rule of thumb that comedians, in person, are often rather glum, as if laughter were a currency too precious to be squandered on everyday life. Caroline Quentin is the glorious exception. The star of Men Behaving Badly, Jonathan Creek and Life Begins laughs a lot, great generous guffaws that warm the room.
Bashing prissy hotel cushions into a comfier configuration, she tucks her legs under her and gives the impression that nothing could be nicer, first thing on a Monday, than talking about the third series of sitcom Life of Riley.
She has, she agrees, pretty much cornered the "harassed everymum" market - right down to her festive ad campaign for Marks & Spencer food. And as stereotypes go, it suits her just fine. "It's a simple relationship to negotiate with the public," she points out, "but of course it's not 'me'. Because I don't live in a sitcom.
“The 'everymum' persona is quite a comfortable coat to put on, and in a way it protects you. I don't think I'm being deceptive. I like the women I play, so I'm very happy to be identified with them. And, oddly, this strong role identification helps me keep some privacy."
Identification, Quentin believes, is the whole point of the family sitcom. Recognisable situations are pushed to the point of absurdity and, ultimately, a kind of catharsis. "The stuff I do is basically about people being allowed to be a bit rubbish. Once you've all had a laugh about something it allows you to say, 'Well, yes, we're all the same. We're all a bit crap about sex, or childcare' or whatever. And it's comforting.
“I'm not mad keen on comedy that points the finger at people and ridicules them. I don't find that very funny. I like the stuff where you feel better afterwards."
Quentin's own home could scarcely be further from sitcom suburbia. As Maddy in Life of Riley she is the stay-at- home mother stretched thin by the demands of husband, parents, children and stepchildren. In real life, she lives on a smallholding in Devon with her second husband, Sam Farmer (her first was comedian Paul Merton), and their children, Emily, 11, and William, 7.
An affinity with poultry notwithstanding ("Who knew turkeys were so adorable? They turn all red with excitement when they see you coming!"), Quentin is the main breadwinner, while Sam covers the home front, raising children, sheep and the occasional pig.
"Our sort of relationship - the way we function - wouldn't suit everyone," says Quentin. "I think a lot of men wouldn't be able to cope - their egos would be fractured. And a lot of women would struggle with the kind of balance we've struck. We got lucky - we love being together - but we constantly have to redefine our relationship.
"I film Riley in Glasgow for nine or ten weeks at a stretch and of course when you get home, you need to readdress what has happened, because naturally everything is not as you left it. It's so delicate, all that stuff, and I'm very aware that I wouldn't be able to do the whole children -and-career thing - I don't think I'd have gone down the nanny route - if it wasn't for Sam."
Playing stepmum to two teenagers in Life of Riley is, says Quentin, "a joyful kind of dry run". "I love working with the kids on the show. I've known them now for three years and we're really close. We go out and have a laugh and they help me on set when I'm feeling old and can't learn things.
“It fills me full of hope for my future with my own children as the teenage years approach. I know they'll get hormonal, but then, I'm hormonal too - they tolerate my nonsense and if they ever give me any nonsense, I'll tolerate theirs - so it's fine!"
With on-screen hormones hotting up as Maddy's stepdaughter begins the dating game, Quentin, who sits on
the board of the Terence Higgins Trust, a sexual health charity, is determined to address the issue of safe sex in Life of Riley.
"I think we're very coy about sex in this country. I don't know how it is in the rest of Europe or America, but here we're still kind of sniggering behind our hands about so many things. And who are we protecting by not discussing this stuff with teenagers? We can only be protecting ourselves.
“Because it's all out there - chlamydia, for example, is a huge problem for young people. It's really frightening because, left untreated, it can cause infertility. I want to get information out there and if the only way I can do it is through sitcoms or comedy drama, so be it. Humour is the best possible way of starting a conversation most parents leave too late."
While she recently branched out into travel documentary with ITV's Caroline Quentin: a Passage through India ("There's a kind of vogue, isn't there, for sending someone famous somewhere hot?"), Quentin, who turned 50 last year, doesn't expect to break out of the comedy mould any time soon.
"There's no place for me in serious drama," she says. "As a woman, you can be funny and 50, but you can't do much else - unless you're Helen Mirren! I don't know where it's coming from, because audiences come to a show with women in it. Women like watching other women. Men like watching women. So why isn't it fashionable?"
The situation isn't helped, she says, by a media culture where every sign of ageing female flesh is documented and deplored. "What are our daughters supposed to think women are aspiring to? Not having wrinkly knees? Well thank you, the Pankhursts. You worked f***ing hard for that!"
Quentin insists, as only a very pretty woman can, that her own appearance is "no big deal". "I think that, as you get older, you become less focused on yourself and more focused on the people in your life. You've learnt to forgive yourself, because you know that you've screwed up so badly and so often and made such bad choices. Which means that when other people screw up you can, perhaps, be more forgiving.
“But I've always been quite comfortable in my skin, though I think a lot of people haven't wanted me to be. My size fluctuates madly, it's done that for years. My tits," she offers, "are size 18 at the moment and the only really boring thing is that I can't do anything up across them."
There's a half-beat pause as Quentin considers the body parts in question. "Do you know what?" she says, with the air of someone imparting a great truth. "My life is no better when I can do my cardie up!"