The rehearsals are for the latest series of Men Behaving Badly, in which she plays Martin Clunes's long-suffering girlfriend, Dorothy. The photo-shoot was to publicise the television adaptation of An Evening with Gary Lineker, the play that stormed the Edinburgh Fringe in 1991 before going into the West End. Quentin played Monica, a long-suffering wife this time, who, years before Fantasy Football gripped the nation, had a fantasy affair with the nation's best player. The Independent called her 'wonderfully sympathetic and funny'. The film version also stars Clive Owen, the hunk from Chancer ('He's marvellous, an absolute genius, and very handsome and lovely, of course, and I love him'), Martin Clunes, Arthur Smith - her comedian friend who wrote the play for her - and Paul Merton.
There. I've mentioned him. But at least it took two paragraphs to get there. Most articles on Quentin begin with the words 'Mrs Paul Merton'. 'It doesn't bother me at all,' she laughs. 'It's true, I am Mrs Paul Merton. You can write about him if you want. I won't start sending you horrible things in the post. It's got me a lot of - what's the word when people see a lot of you? - exposure, yes. There's no harm in being married to a famous funny man.' Especially when you can out-talk him on Have I Got News for You. But while Merton is always himself, Quentin is a character actress who has worked at both the National and the RSC. Imagine Victoria Wood in character, with dark hair, and you're close.
So what is the story of the rise of Caroline Quentin? ('You make me sound like a loaf]') She is 'in her early thirties', as her agent puts it. She comes from Reigate in Surrey, the youngest of four 'very loud, very funny' girls. She decided that she wanted to be a dancer at the age of three. She was at the Arts Educational boarding school in Tring, Hertfordshire, when her parents divorced. 'It was unpleasant at the time, but there were hundreds of girls at school who supported me. I was very happy there. Acting's the same. The people you work with are like an extended family.' Now her own family is happy too. 'It all turned out for the best in a way.'
At 16 she left school and had a not-all-that-illustrious introduction to showbiz in a seaside variety show in Lowestoft. 'I was one of those girls who stand in the background with sparkly bikinis on.' It didn't suit her, apparently: she describes herself as 'short and dark, with big charlies'. In case you're not familiar with this expression, yes, it does mean what you think it does. After Lowestoft there were years of rep, and 'months and months out of work. It was terrible. I don't know why I didn't just give up. Maybe I'll give up now, just thinking about it.' In 1986 she was in the original production of Les Miserables, in a small, singing part. 'Trevor Nunn was gorgeous, actually. I love him.'
Caroline Quentin loves just about everyone and everything, from Clive Anderson to her primary-school headmaster. 'I loved him. He caught me picking my nose in the corridor once and he didn't say anything.'
But most of all, she loves An Evening with Gary Lineker. 'We filmed it on location in Ibiza and it was bloody marvellous. Funny script, nice actors, it was absolutely the best time in my whole life.'
After years of struggling for roles, her problem now is choosing between them. Which makes it a bit hard to see why she agreed to choreograph Paul Merton and his two straight men in the recent Palladium show. 'It was the hardest job I've ever done. They were crap dancers, basically.'
Are there any plans for a more, well, personal collaboration with Merton? 'What, babies you mean? I've thought about it, but it's just one of those things I never get round to, like the ironing.'
What is in the works is a radio play, Gush, by Ian Hislop, Merton's screen sparring partner. 'It's very funny. It's like a Jeffrey Archer novel.' Er, he's not funny, is he? Not intentionally, anyway. 'He is now. It's like Kane and Abel with jokes. And a good plot and characters.'
Arriving at the rehearsal studios, she is on the move again. 'I'm just about to get out of the taxi. I'm undoing my seatbelt. I can see my comedy chums through the window. I sound like Anneka Rice, don't I?' We're not going to see Quentin presenting a new series of Treasure Hunt? 'No, I'd like to do some more serious drama next. I fancy something heavy, something chunky. Apart from my husband.' Does she mean Mr Caroline Quentin?
'Home Front' ends on Tues (8.30-9pm BBC2). 'The Masterson Inheritance' returns to R4 on 11 June. 'An Evening with Gary Lineker' is on ITV on 14 June.