Meghan Markle's wedding dress will be demure, experts say, but watch out for her party dress

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At her first wedding, Meghan Markle wore a simple strapless pleated white dress. Her “Suits” wedding style leaned more extravagant with an A-line skirt and lace detail. But at Saturday's daytime wedding to Prince Harry, she will keep things traditional with long sleeves and a dramatic train, designers predict.

That is, until she changes into a sexy number for the pair’s private party.

Designer Caroline Castigliano keeps her client list tightly under wraps. She did let it slip to Fox News she is dressing several guests attending the upcoming wedding but, she said, “I can’t say who.” Castigliano also dressed guests for Prince William and Kate’s 2011 nuptials.

The famed designer, who has clients all over Europe, predicts Markle will keep it classic on the big day, while still managing to show off her figure in the slightest way.

“I think she is going to be reasonably traditional in her actual wedding dress,” Castigliano said. “This will all be about her respect for the queen… and everything the royal family stands for. She may make it very much her own in the sense that she may wear something figure-hugging. I think she will wear an all-beaded dress, probably lace, nice long sleeves. For me, I see her in a V-neckline and a very big skirt on the dress. I see her in a beautiful silk veil; definitely a silk veil.

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“She will definitely have the choice of a beautiful tiara that will be loaned from Princess Diana’s collection.”

Castigliano clarified the dress may “skim” Markle’s curves but won’t show too much.

“Too curvy would be out of the question. It will not be revealing. I am absolutely certain. I am sure it will skim around her waistline, but it’s not going to be a [mermaid dress]. It will be subtle… showing just how naturally beautiful she is. And then she will have this massive… train.”

Royal expert Leslie Carroll, who has written six books about the royal family, anticipated Markle’s dress will be modest.

“It has to be long sleeves. She is going to be very covered up,” predicted Caroll, who recently published “American Princess: The Love Story of Meghan Markle and Prince Harry.”

Designer Freya Rose, who is known for her shoe collection – a bridal favorite among stars like Kate Moss and Olivia Paloma –, predicts Markle will opt for an understated dress.

“I don’t think she is going to go for anything ostentatious,” Rose told us. “Her style is generally quite simple and unfussy, and maybe a little bit [bohemian] at heart. I think she will have elements of some beautiful details – in the tiara or buckles or with monogramed features – but I think the dress itself will be quite understated.”

On her feet, Rose expects Markle to wear pumps, also known as court shoes.

“The shoe itself will be kept very classic,” she insisted. “We’d like to see some detailing, maybe she will have a beautiful monogramed heel or a buckle that’s been made by a jeweler. I think it will be kept fairly simple. It will probably be a court shoe since it is a formal wedding. We’re not going to see strappy sandals. Maybe a 4-inch heel height. She is used to wearing heels.”

But that’s during the day. Castigliano, Caroll and Rose are all certain Markle will change at night for the private reception with 200 close friends being thrown by Harry’s father, Prince Charles.

“In the evening... that’s their friends, I think she will change. Then I think she will get into something much more slinky… lovely and sensual and in a totally different way,” Castigliano said. “I think she will have a really low backless dress… really showing off her fabulous figure.”

Carroll added, “I am sure she will have a second reception dress because that is going to be in the castle and it is private, that will be different.”

Castigliano just hopes the public will get a glimpse of the second dress.

“I do think we will get to see it. I think it will be terribly short,” she said. “There will be street parties everywhere. I presume that in the end they will do a drive when they come back in the evening. At least, that’s what I am hoping, [that] we do get to see it.”

As for the designer's nationality, Castigliano is nearly certain Markle will go with a British designer for her public wedding gown. If not, Castigliano predicted the decision could be frowned upon by the public.

“I believe on this particular occasion… she has to wear British. I think it would be quite a shock [if she did not]. Everybody loves Harry, there’s just a special feeling for him. And I think it’s really important she gets that same love behind her and to get that I think they would expect her to wear a British designer,” she explained.

But London-based designer Kate Halfpenny is hopeful Markle opts to pay homage to an American designer at the wedding, she recently told the Associated Press. Halfpenny also predicted Markle would wear a dress that is “clean and simple.”

"I hope she's got an American brand on, I really do," said Halfpenny, founder of Halfpenny London.