All too quickly our time with Jasckon Lamb (Sir Gary Oldman) and his team of success-impaired agents comes to a close for another year, with the finale of season 5. For some, this season has underwhelmed. The scale has felt smaller than other seasons, despite the fact the plot was about terrorists trying to destabilise the entire country, and thus it lacked some of the larger scale action sequences. However, there has – on the other hand been higher levels of comedy, thanks in part to the shift of focus to the antics of Roddy Ho (Christopher Chung) and Claude Whelen (James Callis) – both of whom induce country-destabilising levels of cringe.

As it’s with Whelan and Ho’s particular failings that we begin the finale episode. For, while the terrorists have achieved their “blind them all” stage of their strategy, the audience’s eyes have been opened wide as to the intricacies of the scheme, and where the failings in the UK side lay – which was largely in the pants of the aforementioned two men. Tara, (Hiba Bennani), the girlfriend of Ho and the object of Whelan’s saviour daddy complex, has managed to pull the wool over both men’s eyes and used their respective blind spots to build the entire terror plot. Utilising Ho’s need to boast and show off, she had persuaded him to show her how he could hack into MI5’s database, where she initiated a piece of code of her own which resulted in a complete blackout of the security agency’s computer system. And utilising Whelan’s need to save a poor vulnerable (and attractive) girl, she managed to convince him to let her walk away from the Park with his blessing.

When Terrorist Tara calls the Park from the Libyan embassy, Whelan’s humiliation reaches a new level when she asks to talk to “someone in authority”, indicating second-desk Diana Taverner (Kirstin Scott Thomas). It’s a triumphant moment that’s been years in coming, when even the terrorists can see that Whelan is out of his depth, and Diana is where the true power lies. It’s backed up in a wonderful exchange with Lamb, who – of course – has figured out the Libyan’s terrorists’ plan to manipulate Whelan, and tells Diana he would have told her sooner but he thought she would enjoy seeing her boss utterly humiliated. 

By now, the entire plot is entirely on the table – or, more accurately, on the screens. The group of Libyan terrorists have implemented a 1 hour countdown, by which time their demands must be met or they will enact the final stage of the plan – a mass killing at a place of worship. Given it’s a Sunday morning, and they have no idea of a location, Diana deduces they must find a way to pay the £100 million that the group have asked for, in case they cannot stop the countdown or locate the target. Things seem pretty hopeless in the Park, but one thread of interest pops up when they investigate the Cayman Islands’ bank account that the terrorists have asked for the money to be paid into, and a familiar name appears.

Peter Judd (Sam West), ex Home Secretary, is that name, and that sleekit, greaser-of-wheels, soon realises his number is up and he has to admit that the terrorists are the very same group he has been negotiating for, to get compensation for the UK’s part in loss of oil money in the country. Slow Horses does this kind of character so well, with Gimball, Whelan and Judd being the prime examples in this season alone – powerful men, full of bravado and superiority, who are reduced to grovelling schoolboys when their lack of competency is exposed. 

While the Park fumbles to figure out what to do in the remaining minutes of the countdown (Whelan’s suggestion of switching the system off and on again is a superb illustration of his usefulness), Slough House is debating their next step. Like any good teacher, Lamb is an expert at letting his pupils come to their own conclusions, and leads the Horses to the realisation that the target is obvious. Or rather, as Lamb says, only obvious to a psychopath, and thus Coe (Tom Brooke) is the first to cotton on to the terrorist’s plan. They are going to, quite literally, return to the scene of the crime and go back to Abbotsfield, where, Lamb helpfully points out, an all faith memorial service will be taking place that morning. 

Meanwhile, at the Libyan embassy, Tara is having a dawning realisation of her own. When Whelan informs her that the UK government will pay the £100 million,Tara wants to end the killing, However, her co-conspirators disagree. The young terrorist (who lost his father) wants to end the killing of innocents, and only to take out those who were part of the problem in the first place; the final two terrorists have no such morals and want simply to make the UK suffer the way Libyans have suffered.

While Coe, Shirley (Aimee-Ffion Edwards) and River (Jack Lowden) rush to Abbotsfield,Lamb and Standish (Saskia Reeves) have a delightful picnic outside the Libyan Embassy, made up of a sausage roll and Lamb baiting Catherine into endangering her own life in an attempt to get to the Dogs before Tara does. Lamb is unspeakably cruel to Standish, yet there is also a sense he sees the real Catherine more than anyone else. When he says “you get a real thrill being in the action, it gives you the rush you used to get when you get arseholed” we know he is bang on the money, and that’s why she willingly walks in front of the Dog’s pulling up outside the Embassy.  He knows her sense of empathy means she feels compelled to help Tara, and there’s  a sense he admires that in her, and has more than a touch of the same drive – but it’s easier to put the blame on Catherine, and mock her for it than have anyone see him as soft. 

When Tara takes Catherine hostage, it’s only moments before it is apparent Lamb had predicted every move she would make. Shooting in the air, letting Standish go and making a run for it comes to an abrupt end as Lamb awaits with his car doors open – echoing the same circumstances the first time she ran from the Dogs at the start of the season – and delivering the killer line of the episode “I would choose prison any day over dating Roddy Ho.”

In Abbotsfield, Lamb’s best agents… and River, are squabbling like children over the best way to intercede, and who is the better shot. Despite the lack of big action sequences this season, this scene and the entire paint pot saga from episode 4 combine to make a different kind of thrilling action sequence, where violence is mixed with equal parts comedy. The combination works expertly to keep things off kilter, which reinforces the moments humour turns to horror.  Nick Mohammed perfectly cranks up the unctuous element of the London Mayor as he quite earnestly quotes The Fast and the Furious 7 in his eulogising speech. The chaos of the alarm; Whelan on the phone insisting to Jaffrey that there will be no attack; the gunfire from the two terrorists; and Shirley and River bickering makes for a breathlessly entertaining denouement – one which is pitch perfectly punctuated by Coe repeatedly, silently, killing the Libyan with swift stabs of his push knife to the neck.

Whilst the Park thinks things are tied up and all that’s left is whose head is going to roll, we know there’s still one Libyan with a grudge running around London with a gun. Visiting his grandfather in the gardens of his care home, River sees his hero move from lucidity to regression and back in the space of moments. It’s painful to watch, particularly as Jonathan Pryce plays the role so convincingly (as he does in the Thursday Murder Club), but it is necessary for us to see how much River is losing the ties of those around him. And even in his haze of dementia, David manages to set River back on the right trail. As David ponders on the joys of watching bees, River realises that the “sting in the tail” his grandfather warned him about had not happened, and that there is one lone bee still at large.

The one thing this season has done more than any other previously is how neatly it has tied every string together, with so many scenes from the first half of the season having a bookend or parallel in this finale. Whelan jogging in the park, is one such scene. Full of the joys of spring because he has made an agreement with Judd that will keep them both in the clear and out of the papers, an assailant who wants more from him than discomfort kills  Claude’s driver, before going after him. First Desk only manages to run from the Libyan, thanks to an errant dog (literal, not figurative), and then an errant Horse, as River manages to reach Whelan in time to save his life

It’s a dream come true for River; he feels he’s finally won Willy Wonka’s golden ticket, and even if a golden handshake isn’t on the cards, at least a “Welcome back into the fold” surely is? River’s heartbreaking plea to Lamb that he is good enough to return to the fold is hard because we know he is, but we also know he’s impulsive and reactive and too often wants to be the lone hero, 

Lamb and Whelan’s final duel in Lamb’s office – performed so fantastically by James Callis and Oldman – is a dance of power that is choreographed beautifully, and becomes much like the sword fight in the Princess Bride when Inigo Montoya and The Dread Pirate Roberts each hold a secret weapon. Whelan’s is that he and Judd have made an arrangement that throws Slough House under the bus but saves them both. . But Lamb, like the Dread Pirate revealing that in fact he too is not left handed – reveals Gimball’s dictaphone. 

Whelan’s earlier conversation with the Gimballs not only ended his blackmail from Dodie, it also gave the audience the intel that would reveal how and why Tara was able to manipulate him, but it also provides the perfect blackmail material for Lamb.That kind of writing is so skilled and so rare. The vast majority of dramas could only dream of such intricate, subtle storybuilding and execution.

Lamb winning the day, and Slough Houses’ safety, is a triumphant end to the season, but as always, the real ending is the emotional punctuation marks we get from River and Lamb. River, finally proving his worth to the Park, loses out again, as his foot in the door from saving Whelan must be sacrificed to save Slough House. And that loss is amplified when we see him call Louisa and leave a message on her voice mail saying that she is the only person he has to talk to. His emotional journey is plummeting downward and it’s fascinating to see where that will take him in the next season.

And Lamb. Miserable, misanthrope, we see is not quite so unmoved as he presents when he ensures the reinstatement of Molly, and the return of Ho and River to Slough House (and his care) before Whelan’s departure. And then in the final moments, as he and Diana insist they never want to hear from each other again, we are let into the secret world of what goes on inside of Lambs socks. How incredible that a single shot can tell us so much, as we see the criss-cross scars on the sole of his foot; scars which tell us that the horror story he told to Devon during their lockdown, of an agent tortured for information he didn’t have and who had to watch his love and their baby killed in front of him, was not only true, but autobiographical. Jackson Lamb, we’ve barely scraped the surface.

Slow Horses is all available now on Apple TV