Downton Abbey: The Grand Finale, the last instalment of the long-running period drama, opens in cinemas Sept. 12 and closes the 15-year saga that began on television in 2010. Cast members on set recalled practical jokes, production challenges and the bittersweet theme of social change that runs through the film as the Crawley family confronts succession, finance and shifting class boundaries.

The film, set in 1930, relocates the story to London’s theatreland and the streets slick with rain, and contains sequences at a county show, a race meeting and a grand ball. It follows familiar themes of inheritance, romance and social upheaval while bringing back several guest stars, including Paul Giamatti, Joely Richardson and Dominic West, with a portrayal of Noël Coward by Arty Froushan.

Cast anecdotes underscored the mixture of precision and mayhem behind the period detail. Jim Carter, who plays the butler Charles Carson, recalled a hunt scene at Highclere Castle that ended in confusion when hounds picked up a fox’s scent and extras riding as country friends pursued the pack. Penelope Wilton, who plays Isobel Merton, said a fish course shot for a dinner scene took two days to film and left the dining room “stinking.”

Actors also described off-duty moments. Wilton remembered playing scenes alongside Dame Maggie Smith as “like playing tennis with someone better than you,” and said the two competed at the word game Bananagrams between takes. Carter said Smith and other cast members amused themselves by sharing online videos of cats during breaks.

The film foregrounds change within the household and the wider society. Carson complains about new habits — silver cleaned with modern cream rather than soap and water — and the film dramatizes the rise of new social roles, with servants moving into positions in the drawing room and on the local county show committee. A central plotline has Lady Mary, played by Michelle Dockery, publicly shamed by scandal over her divorce from Henry Talbot and forced to assert her authority as the family’s heir.

"Carson’s in mourning for the world he’s lost," Carter said, describing his character’s difficulty in adapting to technological and social change. He noted that the household has a new butler, Mr. Parker, but that some traditions remain: "it hasn’t all gone jeans and T-shirts. Yet!"

Dockery said Mary has learned from her formidable grandmother, Violet Crawley, and is prepared to make tough decisions. One dramatic choice in the film has the family considering downsizing from Grantham House to a London flat as a response to financial strain. The narrative treats that move as emblematic of a broader reshaping of aristocratic life during the period.

The production’s dedication to period detail extended to props and wardrobe. The helter-skelter used at the Yorkshire Show was an original piece dating to 1906, and diamond dress clips worn by Dockery at the Petersfield Ball were lent by Mayfair jeweller Bentley & Skinner.

Julian Fellowes, the series’ creator, writer and producer, wrote and produced the final film and has signalled the end of this chapter of Downton. "It feels quite complete," he said, while stopping short of ruling out any future return to the world he created.

The film acknowledges cast members who have died since the television series began. Dame Maggie Smith, who played Violet Crawley, the Dowager Countess of Grantham, died a year ago; the film is dedicated to her memory and contains an arch reference to one of her character’s signature lines about weekends.

The Downton phenomenon began with six television series, several Christmas specials and two prior feature films. Cast members recalled being surprised by the show’s global reach. Wilton said she expected only a couple of series at most; Carter said that while the series did well in Britain, its sustained global popularity was driven in large part by the United States.

The Grand Finale revisits themes that have anchored the franchise from its start: class mobility, the effects of modernity on a landed family and the personal loyalties that bind an extended household. Many scenes hinge on intimate exchanges — an older Lord Grantham seeking Carson’s counsel, Mary confronting the estate’s money problems, and members of the downstairs staff maintaining bonds that survived social upheaval. Lesley Nicol (Mrs. Patmore), Phyllis Logan (Mrs. Hughes), Sophie McShera (Daisy) and Robert James-Collier (Mr. Barrow) remain connected off screen, Carter said, and some cast members still gather socially.

Critics and audiences will see the film as both a period drama and a closing chapter for characters who have been followed since 2010. The Grand Finale aims to balance spectacle — races, balls and West End theatre — with the quieter work of resolving long-running relationships and showing how the Crawleys adapt to a changing world. The film is scheduled to be released in cinemas on Sept. 12.