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Last Updated on August 21, 2026 by Stefanie Hutson

BritBox has released their September premiere schedule, and fair warning – it's a long one. Most of that length comes from the September 15th release of numerous Agatha Christie adaptations – so if you're a mystery fan, you're in luck.

Looking for previous BritBox and Acorn TV US premiere schedules? Check out:

New Shows Coming to BritBox (US) in September 2026

September 3rd Premieres

Showtrial (Season 1) premieres September 3rd

Showtrial, Season 1 (2021 to 2024)

This legal drama follows high-profile criminal cases from arrest through trial, looking at how evidence, public opinion, media coverage, and the personalities involved can shape the course of justice. Each season tells a separate story with a new cast and case, focusing on both the courtroom battle and the people caught up in it.

Season 1 follows Talitha Campbell, the estranged daughter of a wealthy property developer, who's accused of conspiring to murder fellow university student Hannah Ellis. Cleo Roberts, the duty solicitor assigned to Talitha after her arrest, takes on her defense as the case attracts intense media attention and questions about class, privilege, and the assumptions being made about the accused. Season 1 is a five episode binge premiere.

On September 24th, season 2 will be added, with 2 episodes released on the premiere date followed by weekly releases for the remaining three episodes. The second season offers a new case involving climate activist Marcus Calderwood, who's found dying after a roadside hit-and-run and names a police officer as his attacker. The investigation and trial that follow examine whether his death was murder and what motive may have been behind it.

Watch previous seasons HERE.

September 9th Premieres

Monarch of the Glen premieres September 9th

Monarch of the Glen, Seasons 1-3

Set on a Highland estate in Scotland, this classic British TV drama follows Archie MacDonald (Alastair Mackenzie), a young restaurateur who returns home and unexpectedly finds himself responsible for Glenbogle, the financially troubled family estate. Much of the series revolves around Archie’s attempts to keep the property afloat while dealing with his eccentric parents, local residents, romantic complications, and the demands of rural estate life. As someone who's watched at least part of more than 2000 British TV shows, I put this one in my top 10.

Richard Briers (The Good Life) and Susan Hampshire (The Forsyte Saga) play Archie’s parents, Hector and Molly MacDonald, while Dawn Steele (Wild at Heart) stars as Lexie, Alexander Morton (Luther) as estate worker Golly Mackenzie, and Hamish Clark (My Wonderful Life) as Duncan McKay. Other notable cast members in later seasons include Martin Compston (Line of Duty) and Tom Baker (Doctor Who).

The series is also notable for an early acting role from Julian Fellowes, who appears as the aristocratic Lord Kilwillie. Fellowes was still best known as an actor when the programme began, but during its run he won an Academy Award for writing Gosford Park – and later gained fame as the creator of Downton Abbey.

Seasons 1-3 will arrive on September 9th as a binge premiere, and I encourage anyone new to the series to take those early seasons slowly. They're by far the best, and quality drops off as the series nears the final couple seasons (which aren't included in this release, but may very well be coming later).

SEptember 10th Premieres

Cooper and Fry, Season 1 (2025 to present)

Set in the Peak District, the crime drama pairs DC Ben Cooper (Robert James-Collier), a local officer with deep roots in the area, with DC Diane Fry (Mandip Gill), a more reserved detective newly arrived from the city. Their different backgrounds and working styles shape the investigations as they take on murders and other serious crimes across the fictional town of Edendale. Fry’s reasons for coming to the area also remain part of the wider story as the partnership develops. Two hour-long episodes will be released on the premiere date, followed by weekly episodes for the remaining 6.

September 15th Premieres – ‘Eras of Agatha Christie'

September 15th is Dame Agatha Christie's birthday (she'd be 136 if she were still with us!) – and BritBox is celebrating with a lineup of Christie adaptations spanning decades to go along with the new Tommy and Tuppence adaptation.

Tommy & Tuppence premieres September 15th

Tommy & Tuppence (2025)

Set in present-day London, the series brings Agatha Christie’s amateur sleuths Tommy and Tuppence Beresford into a contemporary setting, with Antonia Thomas (The Good Doctor) and Josh Dylan (The Buccaneers) in the lead roles. Tuppence is the more impulsive half of the pair, while Tommy tends to muddle through with determination, and their investigations are shaped as much by their relationship and comic chemistry as by the crimes themselves. The adaptation updates Christie’s characters and world while keeping the playful mystery and romance at the center of their partnership. Two episodes air on the premiere date, followed by one weekly for the next four episodes.

Murder Most Foul premieres September 15th

Murder Most Foul (1964)

In this 1964 mystery, Miss Marple refuses to accept the apparent guilt of a man accused of murder and sets out to investigate for herself. Her search takes her into a struggling theatrical company, where she poses as an actress and begins uncovering blackmail, rivalries, and further deaths among the cast. Margaret Rutherford stars as Miss Marple in an adaptation loosely based on Agatha Christie’s Mrs. McGinty’s Dead.

Agatha Christie’s A Caribbean Mystery premieres September 15th

Agatha Christie's A Caribbean Mystery (1983)

Miss Marple travels to a Caribbean resort expecting a quiet holiday, but her plans change when a fellow guest dies under suspicious circumstances. As she begins looking more closely at the people around her, she uncovers connections that suggest the death may be part of something larger. Helen Hayes stars as Miss Marple in this 1983 adaptation of Agatha Christie’s A Caribbean Mystery.

Murder She Said premieres September 15th

Murder She Said (1962)

Miss Marple becomes convinced she has witnessed a murder from the window of a passing train, even though no body can be found and the police are doubtful. Determined to prove what she saw, she follows the trail to a country estate and goes undercover among the household staff, where further deaths and family secrets complicate the case. Margaret Rutherford stars as Miss Marple in this 1962 adaptation of Agatha Christie’s 4.50 from Paddington.

The Alphabet Murders premieres September 15th

The Alphabet Murders (1966)

Tony Randall stars as Hercule Poirot, who is drawn into the hunt for a killer carrying out murders according to an alphabetical pattern. As the body count rises, Poirot works to identify the logic behind the crimes while contending with a less-than-helpful British intelligence officer. Based on Agatha Christie’s The ABC Murders, the 1966 film takes a more comic approach to the detective and the case.

Murder at the Gallop premieres September 15th

Murder at the Gallop (1963)

Margaret Rutherford returns as Miss Marple, who becomes suspicious after the sudden death of a wealthy recluse and begins looking more closely at the relatives who stand to inherit. Her investigation leads her to a country hotel, where further deaths suggest the original incident was no accident. The 1963 film is loosely based on Agatha Christie’s After the Funeral.

Murder Ahoy (1964)

Margaret Rutherford stars as Miss Marple, who becomes suspicious when a fellow trustee dies and the death is dismissed as natural. Her investigation takes her aboard a naval training ship, where she uncovers theft, concealed motives, and a growing list of suspects as further deaths follow. Unlike the other Rutherford films, the 1964 mystery was not adapted from an Agatha Christie novel.

Agatha Christie's Murder is Easy (1982)

An American computer expert visiting England becomes involved in a murder investigation after meeting an elderly woman on a train to London. She tells him she suspects that several deaths in her village were no accidents and is on her way to report the killer to Scotland Yard, but she is killed before she can do so. He then travels to the village and begins looking into the deaths himself, trying to determine who may be responsible.

Thirteen at Dinner premieres September 15th

Agatha Christie's Thirteen at Dinner (1985)

Hercule Poirot investigates after an English nobleman is murdered, drawing him into a case involving an American actress and a young actor whose lives are tied to the victim. As further deaths complicate the investigation, Poirot works through a web of identities, relationships, and possible motives. Peter Ustinov stars as Poirot, with Faye Dunaway in a dual role, in this 1985 adaptation of Agatha Christie’s Lord Edgware Dies.

September 16th Premieres

Great Estates from Above (2025)

Narrated by Bessie Carter (Outrageous, Bridgerton), the series explores some of Britain’s grandest country houses and palaces from both the air and the ground. Alongside sweeping views of the estates and surrounding landscapes, it looks at the history, architecture, and people connected with these remarkable properties. Binge premiere of all four hour-long episodes.

September 28th Premieres

Richard Osman's House of Games

Hosted by Richard Osman, the game show pits four celebrity contestants against one another across a changing selection of quizzes, word games, and puzzles. Each round tests a different mix of general knowledge, logic, and quick thinking, with points accumulated over the course of the episode.

BBC Select Offerings (Included with BritBox Premier)

September 1, 2026: Inside the Mind of Agatha Christie | Available in North America | 1 x 60’ – A close look into Agatha Christie's inner world. Explore her vast archive of personal notebooks, expert interviews, and rare and personal testimony from her descendants to get into the mind of the greatest writer of our time.
September 1, 2026: Agatha Christie’s England | Available in North America | 1 x 60’ – Explore the real-life magical places that inspired Agatha Christie's stories, from the sleepy seaside chocolate box villages she lived in as a child to the luxury hotels and trains she visited as an adult.
September 3, 2026: Antiques Roadshow S49 | North America Premiere | 20 x 60’ | Released 2x On Premiere, Then Weekly – Amazing items, poignant stories, beautiful locations. Fiona Bruce and the experts uncover fascinating family and social history embodied in priceless, personal and peculiar items. The season premiere features unique access to Windsor Castle and personal items belonging to Queen Elizabeth II. *Please note this title has moved from its originally slated August 20, 2026 premiere date.
September 10, 2026: Seven Wonders of the Ancient World S1 | North America Premiere | 3 x 60’ | Released Weekly – Bettany Hughes begins her adventure in Egypt, visiting the remarkable Great Pyramid at Giza and discovering its hidden chambers before heading to the world’s first ever skyscraper, the ingenious Lighthouse of Alexandria. Episodes include an augmented reality option where viewers will be able to virtually travel to moments in time to explore, learn, and see these sites.
September 10, 2026: The Secret Life of Rockpools | Available in North America | 1 x 50’ – Paleontologist Richard Fortey discovers the hidden world of rock pools alongside leading marine biologists. From labs to UK coastlines, he explores the surprising behaviors and resilience of extraordinary intertidal creatures.
September 12, 2026: The Travel Show S9 | North America Premiere | 7 x 25’ | Released Weekly – Discover and experience the best destinations around the globe with the Travel Show team.
September 17, 2026: The Mystery of Dark Energy | Available in North America | 1 x 50’ – An investigation of dark energy, the mysterious force that is unexpectedly causing the universe's expansion to speed up. Its very existence calls into question Albert Einstein's general theory of relativity, the cornerstone of modern physics.
September 24, 2026: Bill Bailey’s Vietnam Adventure S1 | North America Premiere | 6 x 60’ | Released All at Once – Bill Bailey travels to Vietnam on the 50th anniversary of the withdrawal of US forces from Saigon. Immersing himself in its rich culture, stunning landscapes and complex history, he uncovers what makes this fascinating country tick.
September 24, 2026: The Art of Turkish Tiles | Available in North America | 1 x 25’ – Cultural historian Janina Ramirez unearths the story behind the ornate Turkish ceramics known as Iznik tiles. Captivating in their complexity, the tiles adorn some of Turkey's most beautiful buildings and museums around the world.
September 29, 2026: The Secret Life of Trees S1 | *Now Available in Canada, Already Available in United States | 3 x 60’ | Released All at Once – A look at how trees communicate and care for each other; how they survive from seedling to mature giant, and what humans can learn from them.

More British TV Shows to Keep You Busy…

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