Slow Horses, season 4 review: Gary Oldman’s faultless spy thriller is as wildly entertaining as ever

Apple TV+’s superb adaptation of Mick Herron’s novels hinges on a terrific cast and sizzling dialogue

Gary Oldman recently described Slow Horses (Apple TV+) as “the PG Tips, Tesco’s version” of espionage. Both are rather more fragrant than his character, Jackson Lamb, but you get the drift. 
We’re into series four now and there is no drop in quality. If anything, each series improves slightly on the last. Watching it is pure pleasure. There isn’t a wasted scene or a duff piece of dialogue. Every performance is perfectly calibrated, with Kristin Scott Thomas’s crisp MI5 deputy and Jack Lowden’s dynamic agent – the Tesco Tom Cruise? – as counterbalance to the slovenly Lamb.
How slovenly is he these days? Well, one scene is devoted to the act of him getting up from the sofa to answer the phone. For the viewer, this is a grossly sensory experience: visual (the camera lingers on on the holes in his socks and the gut hanging out of his shirt), auditory (not just Lamb’s grunts and groans, but the sound of his greasy form parting ways with the leather couch), and olfactory (ok, you can’t actually smell the mix of stale booze, fags and kebab grease through your screen, but you will think you can). 
What I would give for Lamb to inhabit the real world, so we could hear his thoughts on Keir Starmer’s proposed smoking ban. These scenes slot effortlessly into the action thriller side of things, led by River Cartwright (Lowden) as an agent who kills people but throws up afterwards. 
The clever thing about this show is that it’s a spy caper in which implausible things happen, yet River behaves in an entirely plausible manner. We slip back comfortably into the lives of Slough House’s losers, misfits and boozers, all serving time in Lamb’s department after being banished from the main office for various disgraces. “Has anyone offered you tea or coffee?” Lamb asks a visitor, who replies that they haven’t. “Just as well,” shrugs Lamb, “I think there’s something dead in the water tank.” 
There are entertaining new characters too: The Thick of It’s Joanna Scanlan arrives as an efficient manager who appals Lamb by tidying up his office; James Callis is the floundering new “First Desk” MI5 boss. Hugo Weaving is cast as a villain, but I can’t say too much about him. I can’t say too much about the plot at all, really, because I don’t want to spoil it for you. 
But the first episode begins with the bombing of a London shopping centre at Christmas, before we move to the country home of River’s grandfather, David (Jonathan Pryce), where he confronts an intruder. Or does he? David, a former spymaster, is showing early signs of dementia. River’s concerns about this, and Pryce’s touching performance, give this series of the show added heart. 
Not that Lamb has much sympathy for his old boss, or indeed for anyone, including a murder victim (“bullet to the face, literally wiped the annoying look off it”). This lack of sentimentality is one of the many things that makes Lamb such a glorious character. 
A cool new head of security, played by Ruth Bradley, thinks she has Lamb’s number. “I know you’re not the shambling fool you appear,” she tells him. But the rest of us knew that right from the start. 
Season four begins on Apple TV+ today, with each episode arriving weekly