Slow Horses season six is branded the 'best one yet' as Jackson Lamb's 'band of loveable losers' return in 'consistently stellar' MI5 drama

Slow Horses returns to Apple TV on September 16, and season six of the MI5 drama is racking up rave reviews. 

Based on Joe Country and Slough House, the sixth and seventh in Mick Herron’s book series, the new run of episodes are the first penned by Gaby Chiappe, who has taken over as head writer from original showrunner Will Smith.

Whilst there is a changing of the guard behind the scenes, season six sees some familiar faces return to Slough House, thanks to a dramatic, twisty storyline. 

Someone is killing off anybody connected to Slough House with the first episode opening with the shock demise of a familiar face. 

Meanwhile those misfit intelligence officers still employed, and alive, are dealing with a frustrating delay to their paychecks. When Jackson Lamb (Gary Oldman) investigates he discovers he and his team have been mysteriously wiped from the MI5 database. 

Writing for The Times, Ben Dowell has declared series six 'might just be the best yet, even if the mood is decidedly gloomy in Slough House'.

'There is thrilling storytelling and some deftly applied comedy, and it’s always lifted whenever Oldman is on screen,' Dowell continues before singling out 'excellent new character' Reece Nesmith, played by Lenny Rush.

Brian Tallerico for RogerEbert.com agreed that it 'might be its best outing to date', praising the show's pace. 

'There’s no 6-episode anything on television this year that hums like the sixth season of Slow Horses, an outing that’s entertaining, suspenseful, and honestly moving.'

'After season five, I was a little concerned “Horses” was losing its cadence; now, I’m ready to watch it for another decade.'   

Nicole Gallucci for Decider.com pointed out that the show's decision to make back-to-back seasons – with the writers working on scripts for the upcoming season while filming – really pays off this season. 

'It consistently cements itself as one of television’s most compelling, high-quality shows' Gallucci said. 

'So it should come as no surprise that less than a year after Season 5’s finale aired, Slow Horses Season 6 is another masterpiece that raises the bar with sharp writing, standout performances, and deliciously dark humor.'

Carly Lane for Collider praised the decision to bring back old faces as a reward for loyal, longstanding viewers. 

'Season 6's resurrection of past fan-favorites is one of the reasons it's both thrilling and surprisingly comforting to watch,' said Lane, adding that these episodes are 'inextricably connected to some of the show's biggest moments to date'.

'While that means viewers will definitely have to play catch-up on previous seasons rather than trying to jump in from a fresh starting point, it's a narrative choice that rewards the fans who have been devoted to the series since the very beginning.'

She added that Jack Lowden, a frontrunner to take over as Bond, is 'as terrific as ever to watch, calling River Cartwright 'one of his best-ever roles.' 

The Radio Times' David Brown wrote a four star review, declaring that 'once again, it’s a high-wire act of laughs and thrills', adding that 'in its quieter moments, when grudges fester and Lamb abuses his underlings, Slow Horses remains the funniest workplace comedy on television'. 

Stream Slow Horses season six episode one from September 16 on Apple TV. New episodes of the six-part series will drop weekly until October 21.