For a bunch of spies who’ve been sidelined after torpedoing their careers, the Slow Horses aren’t half attracting attention. Someone is bumping off former members, while those still slacking off at Slough House are discovering that their bank balances are looking as unimpressive as their job prospects. Payday has come and gone without a wage packet in sight and, when Jackson Lamb (Gary Oldman) makes enquiries, he finds that he and his team have been wiped from the MI5 database. Well, it’s one way of cutting costs.

Lamb’s response is to go on strike, but don’t expect the series to slow down in a show of solidarity. This latest run combines elements from two of Mick Herron’s novels, Joe Country and Slough House, leaving plenty of ground to cover. Perhaps those in charge fear that, before too long, the rumours will prove true and Jack Lowden may be called away for 007 duties as the new James Bond? For now, though, his alter ego River Cartwright stays in the spotlight, saying goodbye to someone close and hello again to a figure he’d much rather have kept at a distance.

This adaptation - the first without Will Smith in creative control - also makes some notable changes to the source material. Washed-up spook Lech Wicinski, who ought to be making the leap from page to screen round about now, is absent, while the royal sex-scandal plotline from Joe Country has been nixed, perhaps to avoid potentially controversial subject matter. Fans of the books will, though, be correct to suspect that a familiar face is set to make a comeback. Unfortunately, the trailer has needlessly given that away. It means one episode’s cliffhanger is less of a surprise than it should be.

There’s the occasional misstep within the series, too. Would newly promoted First Desk Diana Taverner (Kristin Scott Thomas), for instance, really agree to be interviewed by a populist news network after she’s turned down the offer from its channel boss (Harry Lloyd) of being briefed on their line of questioning?

But such objections to on- and off-screen decision-making are outweighed by the pleasures of this sixth outing. Once again, it’s a high-wire act of laughs and thrills. In its quieter moments, when grudges fester and Lamb abuses his underlings, Slow Horses remains the funniest workplace comedy on television. As for the darkness, that arrives in chilly fashion in the form of assassins Jane (MyAnna Buring) and Jim (Kyle Soller).

Their startling strike rate forces the Slow Horses into the now-familiar posture of hiving off into smaller groups – the old "let’s split up and look for clues" tactic. But despite this routine now coming as standard, the humour survives, most notably in Lamb’s encounters with eyewitness Reece (Lenny Rush), who proves capable of giving as good as he gets. He even matches Lamb fart for fart.

Such displays of noxious flatulence are just one of the ways that the glamour of the spy thriller is punctured. You’d never catch Lamb’s operatives swanning around in tuxedos or upmarket ski lodges. Instead, we’re in drab bowling alleys, soulless motorway services and even the refuelling pit-stop of a Shake Shack. It’s a mundanity that makes the violence more shocking: bloodshed invading these everyday spaces feels almost horribly obscene.

The political dimension also has the tang of the tangible to it, with defence spending becoming as pressing an issue for Taverner as it is for bureaucrats in the real world. Only in her case, she’s simultaneously trying to conceal financial irregularities she’d rather not have exposed. Having finally bagged the top job, the last thing Taverner needs is to be holding a smoking gun. But conscience, as ever, comes in the grimy presence of Lamb, with Oldman clearly still relishing playing the grubby guardian of those principles.

As we’ve now come to expect, the last act finds office politics going out the window – chiefly because the window has been shattered by gunfire and all hell has broken loose. But just when you think the dust has settled, an epilogue delivers one final shock to the system. The final scene leaves viewers as in need of the next series as Lamb is of shower gel and shampoo. But given the speed with which Herron’s back catalogue is being rattled through, hopefully we won’t have long to wait.

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