Slow Horses season 5 review: The funniest outing yet is also the best so far

And it struck a chord with fans.

Things got personal for River thanks to the introduction of his villainous father, Frank, and his grandfather's worsening dementia. Even Mick Herron, the author of the novels on which the series is based, has called it his favourite season.

Naturally then, there will be more eyes on season 5 than there was on its predecessors, meaning greater anticipation and extra pressure. Thankfully, the old adage that pressure makes diamonds certainly rings true here – season 5 is a triumph from start to finish.

Season 5 has been billed as Roddy Ho's season and there's undoubtedly some truth to that. He is certainly the catalyst to many of the season's events, as the team, and in particular Shirley, become suspicious of the fact he somehow has a glamorous new girlfriend.

Shirley discovers this soon after Roddy is almost run down by a truck, and, across town, a seemingly random shooting takes place. While none of these events appear to be linked, it seems Shirley has seen Slow Horses before, and knows something is up.

What follows is a series of increasingly bizarre events taking place right across London, just as the city is in the midst of a contentious mayoral election. Something is going on, and Lamb and his team must investigate. That is, if Diana Taverner and the Park will let them.

As ever, the plotting here is incredibly efficient, zipping along and dropping just enough hints and teases exposing the wider mystery to keep things interesting as you go.

The mayoral election background also brings politics to the fore in a way which has largely been background up until now. Despite the plot of the novel, London Rules, having been written in 2018, the series's approach feels very contemporary.

The effectiveness of this exploration is in no doubt partly down to the work of showrunner Will Smith, who has a background in political comedy on shows like The Thick of It and Veep, and also down to the strong work of guest stars Nick Mohammed and Christopher Villiers, playing rival party leaders Zahar Jaffrey and Dennis Gimball.

Both characters are essentially caricatures, but it's long been clear that's the only real way to successfully tackle politics in the modern era. Rest assured, they are both given just enough complexity to be interesting and believable, yet effectively sent up.

The exact ins and outs of this season's plot may not always be the most innovative or revolutionary, but if we're honest, have they ever been? We don't come to Slow Horses for a story that's going to break the mould of the spy drama, nor do we come to it for cut-and-dried realism.

Instead, we come to the show for some well-crafted genre thrills and, crucially, some laughs. The show has often been billed as Smiley's People or James Bond meets The Office, and that has never been more the case than this time around.

The comedic moments this season come thick and fast, and that's not just because of the emphasis on Roddy. Of course, Christopher Chung is typically brilliant in the role, and it's a joy getting to see him embrace all of the character's greatest absurdities opposite self-serious figures like Kristin Scott Thomas's Diana Taverner and Ruth Bradley's Emma Flyte.

But there are actually plenty of other sources of comedy this time around, with Jack Lowden and Tom Burke in particular doing wonders this season when River and JK Coe are teamed up.

There's a moment featuring the two of them midway through this season which stands out as one of the funniest sequences the show has ever done – book readers will likely know the sequence I'm talking about.

Meanwhile, James Callis remains a phenomenal addition to the cast, as his wildly over-promoted Claude Whelan gets fleshed out and more to do.

Gary Oldman is obviously still a delight – one particular sequence of "weaponised flatulence" has, understandably, already been widely teased.

Many of the more dramatic moments this time around come from Aimee-Ffion Edwards as Shirley, who is still coming to terms with the death of Marcus, as seen at the end of season 4.

It's a storyline which is largely under the surface, but played deftly by Edwards, who also gets to have some fun in some of the season's bigger action set pieces.

As with season 4, this run also has a real sense of forward momentum when it comes to some of the show's longer-running plotlines. These elements may not be quite so central, especially in the early episodes, but by the end of the season you will feel some tangible leaps forward have been made.

Those who may have worried that the show couldn't sustain this after such a propulsive fourth season will have their fears assuaged.

As this is the last season on which Smith has acted as showrunner, it's also worth just taking a beat to recognise what a stellar job he's done with this adaptation.

While there are a host of Apple TV+ shows that have been received with rapturous acclaim for critics, only a handful have significantly broken out within the general public – Ted Lasso and Severance spring to mind.

That Slow Horses has joined this club speaks, of course, to the strength of Herron's source material, but also to the show's reliable release pattern, its superb cast of characters, and the consistently high quality of the writing and directing. To bring it all together is no mean feat, and Smith's work in doing so should be heartily applauded.

Season 6 is already on the way, and here's hoping it can retain the same spark as all of the prior runs. Ever since the beginning of the series, there has been a sense that the next season would be a dud one. Most shows have them, after all. However, so far Slow Horses has shown no signs of slipping up.

Whether this was specifically down to Smith's steady hand at the tiller above all else will become clear next season. Here's hoping that's not the case, and he can successfully hand the show over to new creatives with fans not even sensing a change.

For now, Smith can rest assured that he is leaving the show on a high. There's no doubt that some fans will still prefer season 4, or maybe even one of the previous runs. The show is so consistent, it can be hard to pick.

For my money, season 5 is the best run of Slow Horses yet. It made me gasp, thrilled me throughout, had me laughing out loud, and included one of the most tonally audacious scenes I've seen on TV in a long time. Not bad for a bunch of rejects.

Slow Horses season 5 releases on 25th September 2025 on Apple TV+ – sign up to Apple TV+ now.

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