Crawleys galore! Maggie Smith, Michelle Dockery, and the rest of the Downton cast reunite for a most royal visit on the set of the new film, premiering September 20.

This September, royal mania hits Downton Abbey, and even the lord and ladies succumb to palace obsession.

When creator Lord Julian Fellowes sat down to spin his period drama series into a film, he knew he needed a premise sumptuous enough to satisfy the fans who will have spent nearly four years awaiting Lady Mary’s return.

“You’re looking for a central story that will bind everyone together—affect the characters upstairs, downstairs, and in the village,” says Fellowes, who dreamed up a visit by the king and queen of England to the Crawley estate in 1927, picking up a year and a half after the series finale takes place.

The film’s story line was inspired by an actual royal visit that King George V and Queen Mary made to Wentworth Woodhouse, a country house in Yorkshire, in 1912—to “restate the importance of monarchy,” according to Fellowes.

Like the real trip, Downton Abbey‘s royal extravaganza includes a spectacular parade—created with hundreds of extras in period-precise costumes, cannons, and horses—and white-tie wining and dining.

The event is so large in scale that Carson, the family’s beloved former butler played by Jim Carter, comes out of a palsy-induced retirement to return to Downton and ensure that nary a teaspoon is out of place.

“Mary reaches out for her hero Carson to save the day,” explains Michelle Dockery of her character, who has taken over estate reins. “I love that relationship between Mary and Carson—it’s one of the lovely moments of the film.”

“The family is pulling together in the right direction and the forces of drama are external, which is quite fun.”

Dame Maggie Smith, as the dowager countess and resident queen of lethal quip, gets a new sparring partner in Imelda Staunton, who plays the dowager’s distant cousin Lady Bagshaw.

(A bit of Downton trivia: Staunton is married to Jim Carter in real life.)

Director Michael Engler expects that the cousins locking haughty horns will especially delight Downton diehards.

And fans need not worry for Lady Edith (Laura Carmichael), Lady Mary’s long-suffering sister who ended up marrying a marquess.

“The delicious irony of where we left the TV series was that the most socially vibrant of the family ended up being the one who had the least success in love before,” says Hugh Bonneville, who plays Crawley patriarch Lord Grantham, adding: “Little flashes of sibling rivalries still return when Edith visits. But on the whole, the family is pulling together in the right direction and the forces of drama are actually external, which is quite fun. It’s sort of Downton versus the world.”

GRANDE DAME Maggie Smith as Violet, the Dowager Countess of Grantham, photographed on the set of Downton Abbey, at Shepperton Studios, in Surrey.