Katherine Heigl has got things the wrong way round as far as love and romance are concerned. She got pregnant first in Knocked Up, then she fell in love. But it is only in 27 Dresses that she finally gets to walk down the aisle - 27 times in fact.

Katherine plays Jane, the living, breathing embodiment of the old cliché "always a bridesmaid never a bride".

An eternal romantic who is unrequitedly in love with her boss (Ed Burns), she lives vicariously through her friends' big days, organising hen nights and the like with militaristic attention to detail.

Jane is on first name terms with every wedding caterer in town and, most importantly, she keeps her game face on while forced to wear the most spectacularly bizarre/unflattering outfits that a bride could ever inflict on her maids.

As this is from the pen of the scriptwriter for the Devil Wears Prada, there is understandably rather more emphasis on the clothes than in your average wedding romcom.

"When I first saw them I thought the film makers were taking it too far," says Katherine of Jane's frocky horror show.

"I didn't believe anybody would ask their bridesmaids to wear these, I was shocked and appalled. Then they told me they were real bridesmaids' dresses.

"There are a lot of theme weddings. We had a Gone With The Wind ensemble, a Bahama mama dress in hot pink with big sections or pink and yellow. And we did an underwater-themed wedding. I had had to wear a bathing suit and flowered bathing cap.

"I thought 'no couple would do this' but these weddings happen. Katherine sees Jane as, to an extent, the architect of her own misfortune.

"She's very good at being a bridesmaid and she's always been rewarded with praise and love and attention because she's great at taking care of things. She clearly loves doing it, she's just taking it too far, replacing memories she might make for herself with other people's."

The obligatory wardrobe montage gives audiences a chance to see the normally elegant Katherine dressed up like a pooch's entrée.

The star has been praised for bringing some old-school Hollywood glamour to red carpet occasions. She was one of most stylish women at the Oscars in an off the shoulder red Escada dress that hugged her hour glass figure.

But as Katherine demonstrated when she was filmed legs akimbo, panting her way through childbirth in Knocked Up (in which she played a career girl impregnated by a slacker), she is willing to be humiliated if it'll leave the audience laughing.

"Even when I was little I wanted to be 'that girl' in a romcom and be given the opportunity to be funny. Those are the movies I go and see. Intense dramas depress me for months. I just want to laugh and have a good time. Give me the chance and I will be doing pratfalls and falling into pies and slipping on banana peels.

"I think I am funnier in this than in Knocked Up. I was more of the straight guy in that. This was a real opportunity for me to unleash my comedy, which I haven't really done much of before.

"I have a tendency to go a bit too far, because it's fun for me to ham it up so I have to watch it and rein it in."

Along with Patrick Dempsey, Katherine has been one of the first breakout film starts to emerge from the Grey's Anatomy ensemble.

The soapy medical drama may revolve round the internal angsting of Meredith Grey (Ellen Pompeo) but it is Dempsey who has been re-discovered as a leading man after a period of teen stardom in the 80s and Katherine who is being hailed as heiress apparent to Julia Roberts.

"It's too much pressure to believe that I could ever fill her shoes. In any case I think Julia Roberts herself has the whole Julia Roberts thing well under control," she replies cautiously.

She may be this year's blonde but the 29-year-old actress is no naive newcomer to the movie industry. Born in Washington DC but raised in Connecticut, she was a child model working in catalogues and TV ads before turning to acting.

Her first major role was as Gerard Depardieu's daughter in My Father the Hero, and she followed this by portraying Steven Seagal's imperilled niece in Under Siege 2.

She was a beautiful alien in the cult teen/sci fi drama Roswell. She graduated to adult roles in some largely forgettable TV films before first dipping her toe in broad comedy waters in

The Ringer, where she was the love interest for Jackass's Johnny Knoxville, playing a man trying to fix the Special Olympics.

It was as the model turned medic Izzie Stevens in Grey's that Katherine had casting directors sitting up and taking notice. Knocked Up, the story about beauty meets beast and makes baby, was last year's sleeper hit of the summer.

However, she is smart enough not to let success turn her prettily coifed head.

"I feel like I have just been doing this forever," she says. "I am just glad I am working, because I have had times when I have not worked. There were a lot of lean years."

Born beautiful and into a well to do family to boot, it would be easy to think that, job worries aside, Katherine has enjoyed a charmed life. But when she was just seven the family was left devastated after Katherine's older brother Jason (she is one of four children) was fatally injured in a car accident.

Her parents sought comfort in faith and became Mormons. They eventually divorced 10 years later, only for her mother Nancy to discover she had breast cancer. Katherine supported her through it and the two moved to LA so Nancy could manage Katherine's career.

Katherine's own personal life has run far more smoothly than her screen characters. She married musician Josh Kelly in December after they met two years ago when she was cast in his music video. The two had dinner and, realising she liked him, Katherine, in a very un-Jane like way, made the first move and rang him to tell him so.

She was thinking about her own wedding at the same time as filming 27 Dresses.

"I was looking at wedding photographers and reading bridal magazines and crying at all the pictures, probably because I was imagining myself in them.

"I think marriage is great. The idea of committing to somebody in front of all the people you love most in the world. I like the idea of tradition and the party and the idea that two people are willing to take that chance on one another."

However, she was determined not to embarrass her bridesmaids by forcing them into peach puffballs or Little Bo Peep knock-offs.

"Can you imagine? If I thought they were beautiful and loved them but my bridesmaids were all talking about them the way I'm talking about my dresses in this film and hated them. That would be depressing."