Inside details on Princess Diana's wedding dress and how it was kept under wraps

Saturday 29 July marked 42 years since a shy Lady Diana Spencer walked down the aisle to marry her prince in a fairytale wedding watched by millions around the world. The nursery teaching assistant's life was about to change forever – and hers wasn't the only one.

Elizabeth Emanuel and ex-husband David, designers of the "iconic dress", were about to embark on their own 'rags to riches' story too. In a career spanning four decades, London-born Elizabeth would go on to dress a number of A-list stars including Madonna, Cher, Elizabeth Taylor, Charlize Theron and Priyanka Chopra.

In an exclusive interview with HELLO! Elizabeth, who turned 70 earlier this month, lifts the veil on how the Royal College of Art graduates came to design the world's most famous wedding dress.

A mystery request

The Emanuels' long relationship with Diana began with a mystery request for a blouse from fashion bible Vogue.

"We didn't know at the time that the blouse that we made was going to be worn by Diana. We were told that it was somebody famous and they couldn't tell us the name," says Elizabeth.

That name was of course Lady Diana Spencer, royal bride-to-be, who was selecting outfits for a special photoshoot. So impressed was Diana with the blouse that afterwards she called Elizabeth to say how 'much she loved it' and to arrange an appointment to visit their London studio.

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"I didn't really realise at the time it was done on the phone. I got her name wrong. So when she turned up it was very exciting. We were stunned!"

Diana's 'transformation'

The visit marked the start of a fruitful and reciprocal working relationship.

"[Diana] visited the studio many many times and we got to know her very well," says Elizabeth. "I think she really enjoyed it because it was her first foray into fashion. I don't think she’d really thought about it before. So she would come to our studios and see all the dresses hanging up … and she really liked that.

It was one of these dresses that came to mark an inflection point in how the princess was perceived, by media and public alike.

The dress in question was a little black one she wore when accompanying her future husband to a charity recital at Goldsmith's Hall, just a few months before her big day.

"I think it was a transformation dress because up until that point she’d been wearing very romantic dresses, ball gowns, that kind of thing. And then, when she wore the black dress, she looked like a movie star," says Elizabeth.

"[It had] a plunged neck and had a boned corset. And it was a very grown-up dress. So I think what got the press going crazy about it was she suddenly had this different, Hollywood-starlet look about her, not demure-little-princess in waiting. From that moment on, she became a fashion icon. People and the press started following what she was wearing."

Unveiled!

Diana had asked Elizabeth and David to design her wedding dress prior to stepping out in the black dress - and the frenzied reception guaranteed the commission didn't remain a secret for long.

"She called up and said 'would you do me the honour of making my wedding dress?', says Elizabeth. "She asked us to keep it very, very secret which we did. But I think there was so much interest when she did actually wear the black dress that the press wanted to know who was designing her wedding dress and they had to announce it at that time."

With Elizabeth and David unveiled as the designers of Diana's wedding dress, a new challenge was posed: keeping the dress away from the ravening gaze of the press. To this end, they had to go to extraordinary lengths to prevent anyone from discovering what they were working on.

"Our staff were wonderful and very loyal and didn't talk to anybody. We had the dress stored every night in a metal cabinet guarded by two guards, Jim and Bert. So there was somebody there 24 hours a day and we put shutters on all our windows, and we put false colour threads in the rubbish bins because people were going through our bins," says Elizabeth.

In case the worst did happen to the original, the intrepid designers even had a fallback option.

"We made a back-up dress just in case the secret came out, which fortunately it didn't," says Elizabeth.

Diana the ideal client

Though the designing of the dress, and the circus that went with it, became a 24-7 preoccupation, Diana's trust in the designers and the latitude she gave them made it all worthwhile.

"She was a client who loved what we did. We were free to create what we felt was right. We had an empathy with her and that's really important from a designer's point of view. We had a bond with her. I knew from her reaction that's how she wanted to look," says Elizabeth.

"She was really wonderful to dress, very patient, kind, sweet and excited. There was no hint of anything going on in the background."

The ivory silk and taffeta lace gown was decorated with hand embroidery, sequins and 10,000 pearls. It also featured a 25-foot train – the longest in the history of royal wedding dresses, which could only finally be unrolled at a special final fitting at Buckingham Palace. Watch the moment newlyweds Diana and Charles leave St Paul's after their ceremony...

"It was controversial and very new. There had never been a gown like that before," says Elizabeth. "Mainly because we weren't given any constraints and we were out of college and we just loved designing and flamboyance, and were all into lace and frills and ruffles. It was the age of new romance so we just thought this is fabulous."

Trendsetters

Diana's wedding dress set the trend with brides at the time requesting large puffed sleeves and full skirts.

"We'd only been out of college a couple of years, so it was absolutely huge. And we were really naive. It all happened very fast [but] it was a great reaction," Elizabeth says.

The Emanuels continued to design looks for Diana long after her wedding to Charles, with the new princess even calling the designers to thank them while on her honeymoon.

Unsurprisingly, Elizabeth's memories of both the dress and Diana are laced with pride.

"[It was] a one off, unique dress. And what's amazing is it's become such an iconic dress as well for so many reasons. It represents so many things, that dress - and there'll never be anything like it ever again. And there will never be another Diana."