The BBC’s 'The Assassin' has captivated audiences with its intricate plot, compelling characters, and nail-biting suspense. With the news of two new series confirmed and Tom Hiddleston returning to his iconic role, the appetite for sophisticated spy thrillers is at an all-time high. If you're craving more espionage, intrigue, and high-stakes drama, look no further. We've compiled a list of five of the best British TV spy thrillers to watch – each offering a unique blend of suspense, action, and psychological depth.

1. Spooks (MI-5): This long-running series (2002-2011) offers a realistic and intense look at the inner workings of MI-5, the UK’s counter-intelligence agency. Follow a team of dedicated officers as they confront a range of threats, from terrorism to international espionage. 'Spooks' is renowned for its gritty realism, fast-paced action, and complex characters facing impossible choices. The show’s exploration of moral grey areas and the psychological toll of their work sets it apart, making it a must-watch for any spy thriller fan. The ensemble cast delivers consistently strong performances, and the intricate plots will keep you guessing until the very end.

2. The Hour: Set in the 1950s, 'The Hour' (2011) provides a fascinating glimpse into the world of early British television news. The series follows a team of journalists producing a nightly news program, while also navigating the murky world of Cold War espionage. With a stellar cast including Romola Garai, Julian Sands, and Oona Chaplin, 'The Hour' combines political intrigue with a compelling exploration of personal relationships and the evolving media landscape. The stylish production and sharp writing create a captivating atmosphere of paranoia and suspicion.

3. Bodyguard: This six-part series (2018) was a ratings smash hit, and for good reason. 'Bodyguard' follows a troubled war veteran (Richard Madden) who is assigned to protect the ambitious Home Secretary (Keeley Hawes). As he becomes increasingly protective of his charge, he uncovers a dangerous conspiracy that threatens to destabilize the country. The series is a masterclass in suspense, with relentless action sequences and a gripping plot filled with twists and turns. The performances are uniformly excellent, and the series’ exploration of PTSD and political vulnerability adds depth to the thrilling narrative.

4. Line of Duty: While not strictly a spy thriller in the traditional sense, 'Line of Duty' (2012-2021) shares many of the same DNA. This police procedural focuses on an anti-corruption unit investigating police misconduct. The series is celebrated for its intricate plotting, realistic dialogue, and intense interrogation scenes. 'Line of Duty' keeps viewers on the edge of their seats with its morally ambiguous characters and its unflinching portrayal of institutional failings. The complex web of relationships and hidden agendas will have you questioning everyone’s motives.

5. Slow Horses: Based on the Mick Herron novels, 'Slow Horses' (2022-present) offers a darkly comedic and surprisingly gripping take on the spy genre. The series follows a team of MI5 rejects relegated to a dead-end department known as Slough House. Led by the slovenly and cynical Jackson Lamb (Gary Oldman), they find themselves unexpectedly embroiled in dangerous missions. 'Slow Horses' blends sharp wit, compelling characters, and thrilling action, proving that even the forgotten can play a vital role in national security. The stellar cast and clever writing make it a refreshing and entertaining addition to the spy thriller landscape.

So, whether you’re looking for gritty realism, Cold War intrigue, political suspense, or darkly comedic espionage, there's a British spy thriller on this list to satisfy your craving. Dive in and prepare to be captivated!