Season four of Apple TV+’s hit show Slow Horses is back. Based on the books by Mick Herron, the show follows the exploits of the MI5 agents at Slough House, a base for rejects the intelligence service has cast aside.
Of course, that doesn’t mean there aren’t plots to be foiled. This season sees fan favourites return, as well as a host of new faces – including none other than Hugo Weaving. Here’s our guide to who’s playing who.
Gary Oldman as Jackson Lamb
Oldman is back as Jackson Lamb, the dirty, grumpy and wind-prone head of Slough House’s bunch of MI5 agents. He has a “strong moral code,” even if he doesn’t act like it.
"There’s a jadedness in Lamb, but he’s very loyal to these misfits," Oldman told the Radio Times recently. "When it really comes down to it, he probably cares more than most, although he gives the impression, as a protection, that he doesn’t."
The actor also promised more “breadcrumbs” would be dropped about Lamb’s fateful time in Berlin. “Lamb does change in the different situations,” he added in a cast Q&A. “It’s how he reacts to the different scenarios that come up every season. He's dealing with his team – these losers, these rejects, these misfits – and he’s dealing with their character arcs and how they change.”
Oldman has been on screen for decades. Born in 1958 and trained at RADA, he has appeared in the Harry Potter films as Sirius Black, in the Batman Begins films as Jim Gordon, and as George Smiley in the adaptation of John le Carré’s Tinker Tailor Soldier Spy novel.
Jack Lowden as River Cartwright
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Lowden is back as the troubled agent River, whose relationship with his grandfather David (Jonathan Pryce) forms a key arc of season four.
“By season four, he's mentally not together. And a secret, if you like, reveals itself. Back in the day when he was running the show, David Cartwright was presented with a very personal dilemma and dealt with it the only way he could,” Oldman said about his character. “But those actions have had a knock-on effect, and they have consequences. Lamb, his crew and River are dealing with those consequences from this deal he made many years ago.”
Lowden is a Scottish actor. First appearing on stage – he played Eric Liddell in the 2012 play Chariots of Fire, and won an Olivier Award for his role as Oswald in 2013’s Ghosts, after which, he segued to television. Since 2013, he has appeared in shows like BBC One’s The Gold, as an RAF pilot in Christopher Nolan’s epic film Dunkirk, and in The Rings of Power as Sauron.
Saskia Reeves as Catherine Standish
Also back for season four is Reeves, whose character Catherine is an alcoholic, and has been assigned to Slough House after almost being charged with treason as a result of her boss’s activities. She also happens to be Lamb’s former assistant.
“Catherine is very quick-witted. She’s no slouch,” Reeves told the Guardian. She can give as good as she gets, and [Jackson Lamb] knows that. And she has got a sense of humour. If she only allowed herself to chill out a bit and show it…”
Born in 1961, Reeves has appeared in Close My Eyes (1991), was a series regular on Luther, and has appeared in BBC detective show Shetland.
Kristin Scott Thomas as Diana Taverner
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Scott Thomas returns as MI5’s deputy director general Diana Taverner – but Scott Thomas’s own career is just as impressive. A five-time Bafta and Olivier Award nominee, she has appeared in countless TV shows and films over the years, including 1994’s Four Weddings and A Funeral, 1996’s Mission: Impossible, and Tell No One (2007). She also won the Evening Standard Film Award for Most Promising Newcomer for her work in A Handful of Dust in 1988.
Rosalind Eleazar as Louisa Guy
Louisa is another agent, described in the show notes as “an accomplished and capable agent who has resigned herself to a life with the Horses”.
A RADA trainee, Eleazar has appeared in the BBC series Rellik as Kate, in the ITV series Deep Water, and made her film debut in Armando Iannucci’s film The Personal History of David Copperfield, alongside Dev Patel.
Christopher Chung as Roddy Ho
Former “hacktivist” Roddy is also back, now recruited to MI5 and one of their tech specialists… until he ends up in Slough House.
Australian actor Chung is best known for starring in Slow Horses, but he’s also appeared in the Aussie soap opera Neighbours, Waterloo Road, and Heathers: The Musical.
Kadiff Kirwan as Marcus Longridge
Marcus is, according to the show notes, “a good agent but for a crippling gambling addiction that has wrecked both his career and his marriage”.
Born in Montserrat, Kirwan’s family moved to Antigua after a volcanic eruption destroyed his home – and from there to England. He decided he wanted to be an actor at a young age, and has since appeared in films including Detective Pikachu and My Policeman, as well as TV shows like I May Destroy You, This Is Going to Hurt, and Everyone Else Burns.
Aimee Ffion Edwards as Shirley Dander
Returning for another season is Shirley, a fierce agent who would be highly accomplished if not for a coke habit.
Welsh actress Edwards started her career in Welsh language media, first appearing in 2002 short film Dŵr Dwfn. She appeared as the character Sketch in the TV show Skins, and has since appeared in shows including Sky’s 2023 show Dreamland, 2021 drama War of the Worlds, and Man Like Mobeen.
Tom Brooke as JK Coe
Tom Brooke plays JK Coe, anewcomer and fellow agent. “He’s a man of few words, so we knew we would need an actor who was confident and talented enough to be set in the background but still have a presence,” says writer and producer Will Smith.
English actor Brooke has played Thick Kevin in 2009 film The Boat That Rocked, Bill Wiggins and Andy Apstead in BBC One series Sherlock and Bodyguard, and Fiore in the American series Preacher.
Jonathan Pryce as David Cartwright
Pryce plays David Cartwright, River’s grandfather and a retired senior MI5 officer whose decisions are still having an impact on the Slow Horses today.
Welsh actor Pryce has received two Olivier Awards, two Tony Awards and a knighthood for services to drama. Starting off on stage, he’s appeared in films that range from James Bond film Tomorrow Never Dies in 1997 to 2017’s The Wife with Glenn Close. He has appeared in Wolf Hall, The Crown, and The Two Popes alongside Anthony Hopkins, for which he earned his first Academy Award nomination.
Hugo Weaving as Frank Harkness
An exciting addition to the season four cast is the incomparable Hugo Weaving, who shows up here as a former CIA operative who’s become a mercenary.
“The combination of Frank being a father figure and being a remorseless killer is the most unsettling thing about him. He's an educator but he's also an indoctrinator,” Weaving says about the character. “He’s a weird cross between Fagin and Darth Vader.”
Weaving is probably best known for appearing as Agent Smith in the Matrix films, and as the ageless Elrond in The Lord of the Rings. A British actor who grew up in Australia, his first major role was as cricket captain Douglas Jardine in the Australian series Bodyline in 1984. Since then, he’s appeared in films including V for Vendetta (where he played V), The Hobbit, and as Red Skull in the Marvel Cinematic Universe.
Joanna Scanlan as Moira Tregorian
Actress Joanna Scanlan is another new face to Slow Horses. She’s playing “Queen of the database” Moira, who ends in up Slough House but is confused about the reasons behind her banishment.
“As a character, Moira upsets the apple cart,” says Smith. “She sees herself as above the Slow Horses and reminds Lamb just how much he needs Catherine.” Scanlan, who plays her, is a British actress and writer. She has appeared in films including 2020’s After Love (for which she won a BAFTA), and Bridget Jones’ Baby (2016), but is probably most famous for playing Terri in British satirical series The Thick Of It.
Ruth Bradley as Emma Flyte
Another newcomer to the cast is Ruth Bradley, who will be playing Emma Flyte, MI5’s new head of security.
Irish actress Bradley is best known for playing Emily Merchant in ITV show Primeval (2011) and Karen Voss in sci-fi series Humans (2015–18).
James Callis as Claude Whelan
Newcomer Claude is, according to Smith, “busy putting Diana Taverner’s nose out of joint as the new First Desk at The Park. It’s a high-wire act playing Whelan because you have to believe both that he would be given the job and also that he’s completely out of this depth. James has done that with such flair and instinct.”
Callis has been acting for more than two decades – but he’s best known for playing Bridget Jones’s best friend Tom in the Bridget Jones films, as well as Dr Gaius Baltar in the Battlestar Galactica miniseries, which ran in 2004.
Slow Horses is streaming now on Apple TV+
