Slow Horses showrunner on "emotional" exit and how Nigel Farage inspired season 5 story

“In this series, there were originally three farts,” says Smith. “One came from a story Gary told me – I hope he doesn’t mind me saying – about breaking wind in one of those cavernous restaurants where the sound bounces round the whole place, and there was another at the end. But in the course of the edit, we cut those two so there’s just the one now in episode three, which is a silent fart. So you never actually hear one in season five. It seems an odd thing to say, but we want the farts to be story-led.”

Smith’s CV includes two of the best TV series about politics – the comedies The Thick of It and Veep, both with Armando Iannucci – making him a good fit with author Mick Herron, whose Slow Horses novels always reflect Westminster developments. While earlier series featured the shambolic Boris Johnson-like Peter Judd, season five has Dennis Gimball, a furious Eurosceptic modelled on Nigel Farage.

“In the first book, which came out in 2010, there’s a line that actually predicts the UK leaving Europe,” says Smith. “So Mick’s always had a radar for these things. When the book London Rules came out, it was definitely about Brexit, but the TV version is more about right-wing populism and immigration, which suddenly feels even more topical than when we were making it. There’s not much doubt that Farage is the inspiration for Gimball, although Farage wasn’t even an MP when we made the series.”

London Rules was also prescient in predicting the levels of public unrest and demonstrations that have been seen recently in Britain. “I don’t know how Mick does it. It would be much better if he was wrong about these things.”

There is one main major change from the London Rules story in the new series. “The villains are from North Korea,” Smith explains. “In the book you don’t know who they are at first; we’re in their heads. Whereas, on TV, as soon as you saw them you’d have a sense of where they were from. And, in the book, the villains’ motivation is fear of the Supreme Leader and being put to death. We just wanted to give them more agency.”

On the whole, however, Smith stays close to the books – and in close touch with Herron. “Sometimes, adaptations change pretty much everything. And you think: ‘Oh, you loved the book but didn’t like the story or characters! Why spend all that money buying the rights if you’re going to throw it all out?’ Often, if we get stuck, we go back to the book and ask, ‘What did Mick do?’ We use a lot of his dialogue.”

Smith and Herron aren’t always sure who created a particular line, although one of the TV Lamb’s most famous insults – describing meetings with his staff as being “like explaining Norway to a dog” – is definitely Smith’s. “The reason I know that one is me is that I also used it in The Thick of It and in a stand-up show. Although I’d forgotten about that until I put it in Slow Horses and other writers said, ‘Oh, nice touch, an Easter egg!’ But it wasn’t – it was accidental. So it’s had a few lives, that line, but it was Gary saying it that really made it.”

None of the lines in the next series will be Smith’s, however, as he is stepping down as showrunner. “I feel I’m going out at a good time and leaving the show and the characters in an interesting place,” he says. “I was very emotional. There were tears, but not in front of everyone. Even now, talking about it, I feel the emotion. It’s a very hard thing to let go of.”

So why leave? “It’s a very intense schedule. When I was doing the writers’ room for season five, that was the same time as the edit of season three and the prep and shooting of series four. You’re writing the next series at the same time as rewriting the one that’s being shot and it just became apparent that I wouldn’t be able to have season six ready for when it needed to be. So with great sadness on both sides, I had to stop.”

Gaby Chiappe (Misbehaviour, The Beast Must Die) is taking over as showrunner for season six, with Ben Vanstone (A Gentleman in Moscow) lined up for season seven. Did Smith leave handover notes or take them out to lunch?

“No. I always think it’s better not to be the ghost at the wedding. It’s not something I could do part-time or have oversight of. It was mine... and now it’s theirs.”

The latest issue of Radio Times is out now – subscribe here.

Slow Horses season 5 begins on Apple TV+ on Wednesday 24th September. Seasons 1-4 are available to watch now – sign up to Apple TV+ here.

Check out more of our Drama coverage or visit our TV Guide and Streaming Guide to find out what's on. For more TV recommendations and reviews, listen to The Radio Times Podcast.