If further proof were needed, look no further than this Saturday's BBC1 schedule, which is built round her latest vehicle, the feature-length, opening episode of Jonathan Creek. Like Neil Morrissey, her co-star in Men Behaving Badly, Quentin has a "green light" name, the very mention of which is often enough to get projects off the ground. She is up there in the stratosphere with that other Mrs Merton, the pensionable chat-show hostess (alias Caroline Aherne), and had reached a pitch where, until their recent split, people would talk of Paul Merton as "Mr Caroline Quentin".
Billed as the BBC's big spring drama, Jonathan Creek comes from the pen of David Renwick, who, thanks to One Foot in the Grave, is just about the hottest comedy writer in town. He created it specially for Quentin, having been knocked flat, it seems, by a typically bravura display of hers - in her own front-room. "David came round to discuss a project with Paul," she recalls. "I was meant to be doing 'good wife' work, but I couldn't keep it up and ended up getting drunk and showing off. Six months later, these scripts arrived for me - which cheesed Paul off no end."
Unlike Renwick's most famous work, Jonathan Creek features not a world- weary, out-of-work OAP, but a sassy, young female professional. The twist is... it's a murder mystery. No, don't yawn, or start flicking through the paper for something more interesting. Quentin's character, Maddy, is - perhaps ironically, given recent events - an investigative journalist who specialises in investigating "unsolvable" crimes. Which she does with the help of Creek, an illusionist's assistant played by stand-up comedian Alan Davies.
So far, so familiar. But haven't we had it up to here with detective series? Aren't there already more TV whodunits than suspects in an Agatha Christie novel? And isn't the path that Quentin is treading from comedy to cop-show one that has already been over-trampled by the likes of Robbie Coltrane and David Jason?
Made up with vivid red hair, a blue dress and dangly earrings, Quentin takes a break from filming to have a fag and explain why she has chosen yet another telly 'tec as her means of breaking into mainstream drama. "It's not a detective series," she protests, "it's about social justice." Hmm.
"Maddy is a crusader rather than a hard cow. She gets fascinated by why people get put away, but she's not a female Morse. She's more like Columbo, because she wears a raincoat and is funny. But I can't think of another woman like her on television. Jane Tennison in Prime Suspect is a very strong woman, but you don't see her having a laugh much."
It's true that jokes are the saving grace of Jonathan Creek, lifting it above the usual beat of tyre-squealing, "you're nicked", "go-go-go" detective dramas into a more imaginative and quirky realm. In her first scene, Maddy is quizzing a police officer about a woman found hanged with thick copper wire in a cell. "I was wondering where she might have got hold of it? From a thick copper possibly?"
Later, to gain access to a suspect, she kits out an unhappy Jonathan in the guise of a TV cameraman. "It's called a Steadicam," she says of the bulky equipment, "it's supposed to eliminate jerks." "So does Clint Eastwood," he replies, "but I wouldn't want him strapped to my chest for the afternoon."
But what distinguishes the show is a characteristically strong performance by Quentin: Maddy might almost have the word "feisty" branded on her forehead, and when Jonathan accidentally jabs her hand with a cocktail-stick, her look could grill a sausage at 50 paces. Quentin reckons Maddy is so tenacious she's "half woman, half Jack Russell. She's very volatile, and has a short fuse if she thinks someone's being a pain in the arse."
When she lists Maddy's qualities - "forceful, outspoken, impetuous, capable, bright, funny, difficult" - she could just as easily be talking about herself. Quentin is all those things and more: a presence giving off more sparks than a Guy Fawkes Night bonfire. Remember the zest with which she played up to the role of bickering wife opposite Merton on Have I Got News for You? Or the ker-pow with which she zaps boyfriend Gary's macho preening (c/o Martin Clunes) in Men Behaving Badly? "People always warm to Caroline," says Alan Davies, her co-star in Jonathan Creek, "because she's cheeky and she's not afraid to let her thoughts come out."
You can say that again. Few other actresses would have had the balls to fight their side - and win - in a dispute over the pay disparity between male and female stars on Men Behaving Badly. "Leslie [Ash] and I thought it was time to have equal pay," Quentin asserts. "It all got rather overexcited in the reporting, but I just thought, 'Hang on a minute, we seem to be working the same hours'."
Beryl Vertue, the producer of Men Behaving Badly, testifies to Quentin's ballsiness. She remembers auditioning the actress for the part of Gary's girlfriend, Dorothy. "Just talking to her, she had this strength of character and direct way of speaking which is very Dorothy. We didn't dislike her for it."
But doesn't that sometimes spill over into what men like to call "ball- breaking behaviour"? "No," Vertue insists. "She's a very strong person, and she does have strong opinions. But having strong opinions is not the same as being opinionated. She used to have more strong feminist views, but that's worn off a bit. The strong feminist movement has worn off a bit, too."
How, though, does any woman (card-carrying feminist or not) put up with the orgy of laddery and lager that constitutes each half-hour episode of Men Behaving Badly? "I have mixed feelings about whether or not it's PC," Quentin admits. "But you do hear the other argument, and women do achieve a lot in it. It's not all beer-drinking and arse jokes." (Shagging and vomiting play their part, too.)
Before a sixth series of Men Behaving Badly starts shooting later this year, Quentin is preparing to spend more time with her novel (commissioned by Penguin). So many comedians are now putting pen to paper, the Perrier Award and the Booker Prize must be planning a merger.
In the meantime, like a more vibrant version of John Major, she is lying low, out of the sight of prying hacks. Her one fear for Jonathan Creek is that "it might raise the standing of journalists. God knows, if I'm responsible for that, I'll pack it in tomorrow," she jokes. With feeling.
'Jonathan Creek' starts Saturday at 8.10pm on BBC1Reuse content