Diana's dressmaker predicts Kate Middleton's wedding dress will have "edgy" details

(CBS/AP) LONDON -- Only a select few know which designer Kate Middleton has chosen to design her royal wedding gown, but at least one person - dressmaker Elizabeth Emanuel - can relate to what that person is going through.

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Emanuel, who co-designed the most famous wedding gown in the world, the one worn by Princess Diana on her wedding to Prince Charles in 1981, believes Middleton's mystery designer is probably more than a bit anxious as the April 29 royal wedding approaches.

"I'm sure they are nervous now," Emanuel told The Associated Press. "It's such a big event, with billions watching, you cannot make mistakes. There is no second chance, it has to be perfect."

Emanuel and her ex-husband David triumphed in their own pressure-packed moment, coming up with a showstopping gown that transformed Diana from a little-known nursery school teacher into a glamorous princess. The dress, which set trends throughout the globe, was groundbreaking for its tight bodice, cinched waist and what seemed like miles and miles of taffeta, silk and lace.

"It was perfect for the '80s, but not for today," Emanuel said of her most famous work, which is currently on public display at the Grand Rapids Art Museum, in Kansas City, MO.

There have been leaks suggesting that Sarah Burton, creative director of the Alexander McQueen house, won the coveted commission, but she has denied the reports - though some believe she may be covering up her involvement to maintain secrecy.

Emanuel predicts Middleton, with her long, lean figure, has likely chosen a classic design with some distinctive "edgy" detailing or feature to make the gown memorable.

She thinks Middleton's designer has most likely moved beyond the planning phase and is now cutting the actual fabric in a nerve-wracking, unforgiving process that can become quite expensive if an error is made and some of the pricey material ruined.

Emanuel remembers her own time in the spotlight as a blur. She and David worked around the clock, even making the bridesmaids' dresses and backup gowns for emergency use by Diana in case the press discovered the real design ahead of time.

They were so worried that something might go wrong that they made an "overskirt" that could be worn on top of the real skirt in case someone accidentally spilled juice or coffee on Diana as she was dressing for the ceremony.

There were endless fittings with the incredible shrinking bride - Diana lost so much weight in the weeks before the ceremony that the designers had to make several successively smaller bodices. She had a 23-inch waist by her wedding day.

Emanuel, 57, said as the wedding date neared she started to worry that the gown's 25-foot train would separate from the rest of the dress as Diana entered St. Paul's Cathedral. She feared she would be remembered as the woman who designed the dress that fell apart.

Emanuel used safety pins, hooks and stitches to secure the train and make sure calamity didn't strike.

"We made a parasol in case it rained," she said. "Actually two: one ivory, one white, so the umbrella maker wouldn't know the color of the dress."

She remembers reporters constantly begging her for information, making up sob stories about how they would be fired if they didn't find out details about the dress.

That was in the quaint, pre-Internet era. Today, Emanuel said, the pressure is even more intense and the need for secrecy even higher because anyone with a camera phone could flummox the palace's best laid plans if they get a shot of Middleton entering a design salon for a gown fitting

She adds that fittings are most likely taking place at one of the royal palaces in a secure environment, because the design studios are likely staked out by the ultra-competitive British press.

"It's got to be a surprise, that's the whole thing," Emanuel said. "Bit by bit, all the details of the wedding are being released, and that's the last thing, and everyone wants to know."

She had faith that the designer - expected to be British - will engineer a showstopper.

"I'm sure it will be a fantastic surprise when she gets out of the car; that's what everyone's waiting for," she said.