Slow Horses showrunner talks potential 9 seasons – but has eye on spin-off

With each season following an each book in the series and with season 5 already green lit by Apple TV+, there could be more on the horizon if the streamer are interested.

In a new interview with The Hollywood Reporter, Smith said he would want to create nine seasons, with the Slow Horses story spanning across nine books.

"I think Mick [Herron] is writing the ninth now, but we'll have to see what happens," he explained.

"Depends on what Apple wants and what the appetite is, but I definitely have the kind of leave-them-wanting-more rather than the outstay-your-welcome instinct. But the world of the show is there to be mined."

But nine seasons isn't all Smith has on his mind, with him sharing his interest on bringing a spin-off series to life, based on Herron's book The Secret Hours, which delves into the backstory of Lamb.

"He [Herron] brings in all these other existing characters," Smith told the publication.

"It's a wonderful book that I think there's definitely an opportunity to do a shorter-run [series] or a film or something. I know Gary wants to keep going for as long as he's asked. He loves playing the character."

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Not much is known about what season 4 will entail, with the plot being kept under wraps, however there is a slight teaser.

Based on the synopsis, the new season will open with "a bombing that detonates personal secrets, rocking the already unstable foundations of Slough House".

Season 4 is based on on Herron's Spook Street book, with the novel's blurb potentially revealing slightly more about the season.

The blurb for the book reads: "20 years retired from the Intelligence Service, David Cartwright still knows where all the bones are buried. But when he forgets that secrets are supposed to stay hidden, there's suddenly a target on his back.

"The 'Old Bastard' raised his grandson to be a hero, not a slow horse. Now, far from joining the myths and legends of Spook Street, River Cartwright is part of Jackson Lamb's team of pen-pushing no-hopers at Slough House. Which doesn't mean he won't ditch everything and go rogue when his grandfather comes under threat.

"Lamb worked with Cartwright back in the day, and knows better than most that this is no innocent old man. So when a panic button raises the alarm at Intelligence Service HQ, it's Lamb who's called on to identify the body. And it's Lamb who'll do whatever's necessary to protect an agent in peril."

Slow Horses season 4 will stream on Apple TV+ from Wednesday 4th September – sign up to Apple TV+ now.

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