"I don't think you can repeat her 'performance' at the wedding," says the actress

By Alison Schwartz and Jeffrey Slonim
Updated August 10, 2011 09:15 AM
Credit: Jim Spellman/WireImage; Matt Baron/Pool/Photoshot/AdMedia

For Alice St. Clair, embracing her inner duchess to portray Catherine, Duchess of Cambridge is all fun and games – literally.

St. Clair, the the latest actress to fill Middleton’s (sensible) shoes, tells PEOPLE she got to take on the Queen in a Wii tennis match on the Hallmark Channel’s William and Catherine: A Royal Romance – a scene she says is based on real life.

“They really do [play],” she tells PEOPLE. “Everything in the script is fact.”

PHOTOS: Kate Middleton Tours Royal Wedding Dress Exhibit

And although Middleton and the Queen’s sporty pastime will play out in the film, which debuts Aug. 27, St. Clair says there’s one major moment she won’t act out: the royal wedding itself.

“We didn’t do those scenes, luckily,” she says. “I don’t think you can repeat her ‘performance’ at the wedding.”

The film, a biopic prequel that follows Lifetime’s made-for-TV movie, opens the moment Kate meets Prince William at the University of St. Andrews.

“A lot of it was using my own experiences about being a 20-year-old,” the budding actress explains. “I didn’t try too hard to mimic her.”

With a few pitch adjustments – “My voice is quite husky,” she says – and a princess-worthy wardrobe, St. Clair “changed into [Kate] without really even realizing it.”

Her prince is played by Dan Amboyer, a fellow Hollywood newcomer, whom she says lives up to William’s double-smooching standards.

“[He’s] a great kisser,” she says. “My boyfriend would be jealous.”

And although St. Clair hasn’t met the Duchess, she does have her own Palace connection. Her father is the head of security for the royal family, she says, which means her family gets a taste of royalty around the holidays.

As she says, “I think they give out a Christmas pudding every year.”