Transcript for How Diana, Kate and Meghan created their own unique fashion statements
Reporter: From the Kate Middleton effect, to the Markle sparkle, the royal influence on fashion is felt around the world. Kate is worth $1.4 billion a year to the British fashion industry. Meghan is now being called the biggest fashion influencer in the world. She's probably going to be worth even more to the British fashion industry. What can you say about the Markle effect on fashion? Meghan Markle already is the most wonderful ambassador for fashion. Reporter: Two women, two very different styles, both with unmatched global reach. Any style they wear selling out in minutes. They both are very contemporary. One much more traditional. And one a little bit edgier. Kate Middleton's style is more conservative. I think it's more British. Meghan's style -- it has a greater sense of informality, a little bit funkier. I have what I call Wakely wardrobe -- Reporter: Amanda Wakely the face behind some of the Royals' most fashionable moments. Who do you think would look beautiful in this? I think -- you're trying to trick me. Reporter: Her first brush with the firm came in 1993 with princess Diana in a skirt suit. When she first emerged announcing her retirement what did that do to your business? I had no idea that she was going to be wearing that suit for that occasion. What was your reaction? It was -- oh my god. Reporter: A royal favorite, Wakely's gone on to dress both Kate Middleton and Meghan Markle. It all started with princess Diana. To now be providing designs for her daughters-in-law, it's kind of come full circle for you. Yes, that feels really wonderful. It breaks my heart that she's not here to see it all. Because -- she'd be loving it. Reporter: Diana revolutionized royal fashion, breaking with tradition and thrusting royal style into the spotlight, paving the way for her future daughters-in-law. I think her choices of those dresses kind of gave us a new way of defining what royal glamor could be. Prince Charles himself has taken a publicity back seat to his wife's trend-setting clothes -- Diana led the way with so much fashion. It was amazing how the world reacted to what she wore. She became this extraordinary design icon. Reporter: The boundary-pushing legacy now being carried out by Meghan Markle, who has attended events wearing sky-high ripped jeans, and without panty hose, a royal staple. I was fascinated by the hat that she wore at a recent event. It had this kind of, you know, sort of California vibe to it. More casual, even for a dress hat. She also has a lot more leeway than Kate, future queen consort to the uk. So expect to see Meghan push fashion boundaries in a way we'll never see Kate do. Reporter: In two days Meghan will make her biggest fashion statement yet as she steps into history. Like Diana and Kate before her, the wedding dress will be seen and critiqued by millions all over the world. Meghan is getting married in a stunning gothic chapel. She needs to have a grand dress to match the venue. That's the most important thing. The dress has to match the venue. While she perhaps might instinctively want to go for something fairly simple, she is going to have to take into consideration this incredible atmosphere. Reporter: A 20-year-old Diana donned an extravagant ivory silk taffeta dress. It was ruffles. It was ruffles upon ruffles upon ruffles with a train of ruffles. Reporter: The train, a staggering 25 feet long. And flash forward 30 years later. Kate walking down the aisle in a stunning satin Alexander Mcqueen gown. But the details of Meghan's gown are still a complete secret. At this point, every single designer in the country has been accused of working on this dress in Reporter: British milliner Victoria grant adorned the heads of the well-heeled with epic creations. This is a big part of the British culture. It is, yes. For an American, hats might not be as commonplace. Here, it's very common. Everyone owns hats. Obviously weddings, garden parties, cocktail parties, as well as all the formal occasion wear. Reporter: Fascinators, as they are called, have become something of a fascination for American royal watchers. So fabulous. I love it. Icas. "Nightline" team witnessing history in the making as we stopped by the studio of famed royal hatmaker Philip Tracy. Hello, look at this. A real live English princess. Are you excited about that your hat? I haven't seen it yet. Oh! You know, it's looking good. Trust me. Do you? Yes, I do, always. Reporter: Princess Beatrice dropped by to pick up this head-turning creation for the wedding of her cousin will. Meghan Markle has already tipped her hat to this very British tradition. What hat would you pick out for her? I'd like to see her in something with a little more detail. She could do a little bit of veil. Reporter: Other traditions to watch, the charming custom of young brides maids and pageboys. Most notable, George and Charlotte. And expect some sort of tribute to the late princess Diana. Diana would have been so proud and so happy that Harry is marrying the woman that he loves. Really marrying for love. Reporter: For "Nightline," I'm Paula Faris in London.
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