It may surprise some out there to know that the sitcom Friends ended seven years ago, so constantly is it screened on British television.

So the image of Jennifer Aniston in her best known role as Rachel, the unlucky-in-love quite literal girl-next-door to her loveable castmates is firmly fixed in the popular imagination.

But Horrible Bosses could change all that, as she plays a sex-obsessed dentist keen to get a rise (of some sort) out of her hapless employee Dale (Charlie Day).

It’s a head-turning switch for the 42-year-old actress, and was consequently a challenge she wholeheartedly embraced even as it shocked taste and decency by going so far down the politically incorrect route.

“That was the fun of it,” she nods, “the movie really went for it, it wasn’t ‘sort of Horrible Bosses’, they were really horrible.”

Along with co-stars Kevin Spacey and Colin Farrell, Aniston is part of a trio of hated employers who are targeted by Dale and his pals Nick (Jason Bateman) and Kurt (Jason Sudeikis) in a spectacularly ill-conceived but very funny triple murder plot.

“The first time I read it I thought of casting Jennifer,” explains director Seth Gordon. “I don’t know if that’s good or bad but that’s exactly who I thought of. She’s such a great comedian that I just thought she’d bring a life to it that no-one else could.”

And she certainly does. It’s no particular shock to see Spacey and Farrell playing it mean but Aniston’s ruthless efforts at sexual harassment in the workplace makes for some of the film’s funniest scenes.

“It’s very vulgar and it’s very crude,” she adds, “but that’s what’s fantastic about it, being that outrageous it’s limitless. You just get to have complete abandon and not worry if you’re being inappropriate. I loved that.”

Which is not to say that some of the more outré scenes of flamboyant and scantily dressed comedy were entirely comfortable for her.

“It was a little embarrassing for me to have to basically meet Charlie Day one day, and then do all that stuff. I try to keep fit. I think if you keep in good health and in good shape then those scenes don’t terrify you as much.

“It’s better to consistently stay in good shape so you don’t have to go crazy (in the gym) before filming.”

Speaking to the press along with her male castmates, the noticeable thing is just how many of the questions are directed at Jennifer Aniston, and how adept she is at sidestepping the attempt to elicit something personal out of her. So when she is asked about the stories that she is to take some time off from making movies, she offers only the scantest of details.

“Why am I going to tell you?” she asks in mock outrage. “I’m just going to take a break and not know what I’m going to do, which is the fun part. Travel, and live a little.”

Questioned about the recent casting of her handprints on the Hollywood walk of fame she is similarly succinct.

“It was an unbelievable honour,” she smiles, “wonderful, amazing and a bit surreal.”

A hint at just why she remains so guarded may be gleaned from her response to the enquiry about her views on film reviews – noting perhaps the sometimes brutal reaction she has tended to provoke, a subject touched on last year by actor Rupert Everett who questioned her place on the A-list after a less than successful run of films.

“Film critics today seem to make personal digs rather than constructive critiques of performances,” she says. “It can get very personal.”

That much is undeniable, and whether it has been in reaction to her small screen success, slightly smug ‘because I’m worth it,’ cosmetics commercials or high-profile turns in her private life – including a five-year marriage to Brad Pitt – she has faced some mean-spirited criticism in the past.

Horrible Bosses at least goes some way to redressing that, as it lays bare her goody two-shoes image and suggests a taste for edgier, maybe even darker work in the future. And while she recognises that wo-men form a major part of her following she is at a loss to understand precisely why.

“I don’t know how to answer that question,” she sighs. “I honestly don’t. I love girls – I think that’s why.”

Sitting next to her co-star Jason Bateman cannot resist jumping in at this: “There’s your headline everybody.”

“Yep,” smiles Aniston, resigned to the laddish banter that sums up the mischievous tone of her raucous new comedy: “There, I said it, I love the girls.”