First off, if you aren't watching Slow Horses on Apple TV+...

well then you better get streaming! Slow Horses is a darkly funny espionage drama that follows a team of British intelligence agents who serve in an off-the-books department of MI5 — called Slough House — due to their career-ending mistakes. If you're new to the show or just looking to get started, here's the Season 4 cast as well as the other TV shows and movies you might have seen the actors in before: First up, the show stars Gary Oldman as Jackson Lamb, the brilliant but unsociable leader of the spies: You probably know him as Sirius Black in the Harry Potter series or as Winston Churchill in Darkest Hour : Jack Lowden plays River Cartwright, who is pulled into a conspiracy alongside his grandfather: You might know him from Dunkirk or the BBC miniseries War & Peace : Jonathan Pryce plays David Cartwright, River's grandfather and a retired MI5 officer: You might know him from Pirates of the Caribbean : The Curse of the Black Pearl or Game of Thrones : Kristin Scott Thomas plays Diana Taverner, the second desk at MI5: You might know her from Four Weddings and a Funeral or The English Patient : Hugo Weaving plays Frank Harkness, a former CIA operative and one of the big bads of Season 4: You might know him from The Lord of the Rings: The Fellowship of the Ring or The Matrix : Rosalind Eleazar plays Louisa Guy, a member of Slough House: You might recognize her from Harlots : Saskia Reeves plays Catherine Standis.