London ? Only a handful of insiders know which designer Kate Middleton has chosen to create her top-secret wedding gown, but at least one person — dressmaker Elizabeth Emanuel — understands what that person is going through.

The woman who co-designed the taffeta confection that Princess Diana wore in 1981 when she walked down the aisle to marry Prince Charles 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,” said Emanuel, relaxed and chatty in her central London studio, surrounded by mannequins wearing dramatic handmade wedding gowns. “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 was groundbreaking for its tight bodice, cinched waist and what seemed like miles and miles of taffeta, silk and lace.

Rosemary Harden, director of the Fashion Museum in Bath, England, said the dress set trends throughout the globe.

“It definitely set the tone for 15 to 20 years,” said Harden. “It was something everyone remarked upon — it took people’s breath away. It was the archetypal fairy princess dress, with an incredible quantity of beautiful fabric and beautiful silk and that long train.”