Kate and William's Big Fat Royal Wedding Might Be on Slimmer Side

Nov. 16: Kate Middleton and her fiance Prince William at a press conference discussing their engagement.

With the very modern announcement of Prince William and Kate Middleton’s marriage (via Facebook and Twitter!), experts are expecting a few twists on the traditional royal wedding.

“It’s clearly not going to be the same kind of wedding as Princess Diana’s wedding,” Andrew Roberts, British biographer and historian, tells FOX411.com. “The government isn’t going to shell out vast fortunes for the kind of celebrations that we had in 1981. It’s going to be much more like the Queen’s wedding in 1947, when the Queen had to collect ration vouchers for her wedding dress. It will still be immensely grand, magnificent and a splendid occasion, but it’s not going to be one in which vast amounts of money will be spent.”

The wedding, though not as elaborate as Prince Charles and Princess Diana’s, will be formal.

“There are some ancient traditions that go back to the weddings of the Norman and the Angevins and the Plantagenets kings that you can’t avoid,” Roberts tells FOX411.com.  “For example, you’ll have the Archbishop of Canterbury giving a sermon—that’s not something that everybody would automatically jump at, frankly, in most modern weddings.

“You have the entire diplomatic corps, you’ll have foreign Heads of State, you’ll have the whole of the House of Lords and the House of Commons, you’ll have the leaders of the Armed Forces, the Judiciary—people who aren’t friends of William and Kate’s who will have to be there because this is a very serious and significant state occasion.”

Another way it will be different? Kate’s dress will be more modern and less voluminous than Princess Diana’s, experts say.

“The dress will be nothing like Diana’s,” Andrew Roberts tells FOX411.com. “It would be a disastrous PR move for the Windsors to try on something like that. It was ‘80s—that was the decade of Dallas and shoulder pads. Things have moved on massively—more is not necessarily better when it comes to fashion any longer.”

Celebrity wedding planner Sasha V. Souza echoed Roberts’ sentiments.

“Kate isn’t going to be that cupcake bride,” she said. “Her dress will be very beautiful and detailed with beautiful draping, but it isn’t going to have a 25-foot train.”

“Kate Middleton definitely loves a classic, simple look, whether she’s dressing in a lady-like suit for official royal functions, or a miniskirt from Topshop,” Renata Espinosa, Fashion Wire Daily’s managing editor, tells FOX411.com. “I’m sure plenty of fashion people would love to see her pick Vivienne Westwood or Alexander McQueen, arguably the best British fashion houses, but that seems pretty unlikely, given that this is going to be a highly regimented affair, not a fantasy photo shoot for Vogue.

“For her engagement announcement, she wore one of her favorite designers, Issa, so maybe that’s a hint that she’ll commission her friend Daniella Helayel, the Brazilian-born, London-based designer to do the dress,” Espinosa added. “But for her royal wedding, she may have to hew to official royal demands, so perhaps she’ll opt for someone like Amanda Wakeley, known for her glamorous evening wear, and who was worn by the late Princess Diana.”

One thing that’s for sure, according to Roberts, the wedding won't take place at St. Paul Cathedral, the site of Prince Charles and Princess Diana’s wedding. “The last thing you want is to have the same image of the bride going up the same steps as you had in 1981. So instead, Westminster Abbey, which is where the Royal Family have been getting married and being buried for over a thousand years, is likely to be the place. There will be standing room only in Wesminster Abbey, which sits up to 5,000 people. There will about 4,000 very grand people and about 1,000 very lucky people attending.”

While there’s not much chance of a royal elopement, Souza has a humble suggestion for Kate and Prince William, “I would love to see them running away to Maldives for a small, private ceremony and then return to London for the big wedding. They’re such a private couple, it would take a lot of pressure off them.”

Good luck with that.