Helena Bonham Carter wanted to look the part for the London premiere of her new film `The Wings of the Dove' on Wednesday. Tamsin Blanchard watched the transformation.

Photographs by Jillian Edelstein

4pm The Dorchester Hotel. Helena Bonham Carter, movie star and street urchin, is swigging water from a bottle of Evian, wandering from room to room in the palatial suite that is to be her dressing-room for the evening. She is wearing a pair of baggy trousers held on to her tiny frame by braces, an old jersey top and a pair of grubby white trainers. Her hair is sticking up all over the place and her finely-boned porcelain- pale face is without a single trace of make-up. She smokes in between mouthfuls of water.

"Let's see if it fits before we start," says Helena, stripping down to practical big knickers and a grey Calvin Klein sportsbra. She unzips the pink-edged clothes hanging bag to reveal a candy-pink taffeta corset top and long fish-tail skirt made specially for the star's London Film Festival premiere of her new film, The Wings of the Dove. Across the gold Vivienne Westwood label is another narrow label with the word "special" embroidered in gold thread.

Westwood's business in providing celebrities with gowns to wear to one- off events is growing. She dressed Elizabeth Shue for Leaving Last Vegas, and made another pink confection for Kate Winslet to wear to the Academy Awards earlier in the year.

Helena is tiny, but despite a fitting two days earlier, the skirt and top are even smaller. The dress was made in just 48 hours. It looks as though some some good old-fashioned knee-in-the-small-of-the-back techniques are in order. But then Helena is used to being squeezed into corsetry. She is also used to being dressed completely out of keeping with her own character. Her personal style is famously scruffy. She usually wears just "a bit of make-up with some zit cover-up", and is more interested in comfort than fashion.

Tonight she has just another role to play: "I'm dressing up and pretending to be a movie star," she says. Her comfy clothes will be stuffed into a plastic bag until the morning. The dress, with its decolletage neckline, impossibly small waist and Marilyn style fish-tail skirt with ruffles of glittery net underskirts is pure Hollywood glamour and just the thing. "I'm not innately glamorous. If it was left up to me, I would never choose to wear a dress like this. But this is fantasy time."

4.50pm Make-up artist Louise Constad sets to work while Helena sneaks another cigarette. Constad is a make-up artist to the stars and has covered spots and brushed powder on almost any celebrity you can name, from Faye Dunaway to Tina Turner.

"What a palaver," laughs Helena at the prospect of three hours of primping and preening. She might as well be back on the set of a movie, where she spends lots of time with make-up artists. "You both have to share a sense of humour and a taste in music because you have to spend a lot of time together - I like show tunes," she says. For Wings, Helena spent a total of 10 weeks between hair and make-up filming in London and Venice, where she spent most of the time feeling seasick from too many takes in a moonlit gondola.

Slowly, Helena's public face takes shape. Her eyes are dusted with dark blue shadow and a touch of sparkly glitter and her eyelashes grow thicker and longer with each wave of the mascara wand.

5.55pm "She's not a hairdresser at all: she's going to make a dress now." Helena's regular hairdresser Carol Hemmings is rummaging in a dressing- up box full of velvet flowers, threads of beads, feathers and ribbons. She pulls out a length of pink velvet ribbon, some seed pearls and a needle and thread. She then sets to work sewing short pieces of hair into Helena's own hair. It looks painful. "All that long hair I'm supposed to have, it's actually in Carol's box," says Helena, blue varnish being applied to her nails. The hair-pieces are trimmed to fit in with Helena's own and the tiny pearls are threaded on to single strands.

6.15pm "Hello my angel!" Helena's innately glamorous silver-haired mum, Elena, arrives to escort her to the premiere. She's already seen the film twice. She is dressed in a plum taffeta jacket and skirt made to her own design. Underneath, she is wearing a white ruffled blouse she picked up in Madrid. The suit, she says, is an old faithful. She has worn it to many a premiere.

7.40pm Hair and make-up done, it's time to get dressed. Helena breathes her last free breath for the night and the zip is forced closed. As she looks in the mirror and sees Helena the movie star, there is a ping. "I think something's gone," she cringes. "It might be your vertebrae," jokes Louise. The zip has broken but, thankfully, the buttons hold the corset together. Mum takes a needle and thread just in case and they step out into the cold night, the autograph hunters and the waiting limousine.

"Did she give you an autograph?" asks an onlooker. "No," I reply. "But doesn't she look fabulous?"

`The Wings of the Dove' opens 2 January 1998 nationwide