Matthew and Lady Mary get ready to walk down the aisle in season 3; sneak a peek at her dress and more here!

Forget the royal nuptials. The real wedding of the century belongs to Downton Abbey's Lady Mary (Michelle Dockery, pictured with on-screen father Hugh Bonneville) and Matthew Crawley (Dan Stevens, not pictured). After much on-again, off-again angst, the couple capped off season 2 with a romantic engagement and are ready to walk down the aisle in season 3.

Season 3 kicks off just two months after the proposal, with the Crawleys — including Matthew, left, and in-law Branson (Allen Leech) — preparing for the grand celebration. That's not to say it actually takes place, however. ''We don't start with the wedding necessarily happening,'' teases creator Julian Fellowes, who is well aware of the expectations surrounding this event.

Though Fellowes wouldn't confirm the wedding, it's evident that that the guest list will include Mary's mother and sisters (Dockery, from left, with Elizabeth McGovern, Laura Carmichael, and Jessica Brown Findlay). ''Like the proposal, you can't just go on and on and on with them not getting together,'' he says. ''There does come a moment when you think either they've got to put up or shut up.'' Hear, hear!

To outfit the bride-to-be, costume designer Caroline McCall spent eight weeks conceptualizing and creating the perfect gown: a long-sleeved lace dress fitted with tiny Swarovski crystals and rice pearls that would ultimately become the series' most expensive costume to date. ''Sometimes the character can be quite hard,'' says McCall of Lady Mary. ''I wanted her wedding dress to have a bit of softness. I wanted her to look really romantic, really elegant.''