Slow Horses Season 6 Confirms Olivia Cooke's Return As Sid

Published Aug 18, 2026, 9:08 AM EDT Felipe Rangel is a Movie and TV Journalist ScreenRant. He has been writing about movies and TV since 2021. Felipe joined ScreenRant in 2022, working across different teams, covering everything from breaking news to features to reviews and more. Felipe is a writer who is an avid film and TV fan, with superhero movies and series being his biggest passion. He graduated from college in 2019, having studied Journalism. Before college, he spent a month studying at the Oxford English Centre. His superhero knowledge expands to the comics, with his undergraduate thesis being "Politics Reflected In American Comics." Sign in to your ScreenRant account Slow Horses is welcoming back a familiar face. Slow Horses is one of the most popular spy thriller series in the world. The Apple TV show has also mastered the art of annual releases, going against the common rule of waiting multiple years for new seasons that has led to streaming shows being so criticized. Throughout five seasons so far, Slow Horses' core cast has largely remained the same, anchored by players like Gary Oldman's Jackson Lamb and Jack Lowden's River Cartwright. However, with every new season of Slow Horses, fan-favorite characters debut, die, or leave the show. Now, a popular player is finally making her comeback. The official trailer for Slow Horses season 6 has been released by Apple TV, confirming that Olivia Cooke will reprise her role as Sid Baker. The actress first played Sid in Slow Horses season 1, which was released back in 2022. Since then, Cooke has gone on to become one of the main leads in another hugely successful series, the HBO Game of Thrones spinoff House of the Dragon, where she gives life to Alicent Hightower. As the Slow Horses season 6 trailer shows, Sid will be reunited with Lowden's River, much to his surprise, raising many questions. More to come...