‘Slow Horses’ Season 6 review: Another impeccable season of Britain’s finest caught with its trousers down

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No collection of blundering intelligence operatives on television is quite as magnificently useless as the residents of Slough House. Over five seasons, Jackson Lamb, River Cartwright and the rest of MI5’s human refuse pile have survived bombings, kidnappings, botched extractions, terrorist plots, Russian skulduggery, rogue agents, internal coups, political cover-ups, and an array of other catastrophically bad professional judgements. Yet here we are again, six seasons into Apple TV’s glorious, grubby espionage comedy, and almost nothing has changed (complimentary). Slough House is still populated by its spectacular clown car of disgraced spies, except the bodies turning up around them this season suggest their latest disaster might actually have nothing to do with their own incompetence. For once, somebody other than the Slow Horses may be trying to kill the Slow Horses.

Season 6 opens with David Cartwright dead and River (Jack Lowden) preparing for his funeral. Slough House gets no time to process the funeral before the bodies start piling up. When Struan Loy, the incompetent sad sack Lamb (Gary Oldman) fired back in Season 1, is the first to turn up dead, they soon realise that his death is connected to a series of killings targeting former Slow Horses. Two assassins, played by Kyle Soller and MyAnna Buring, are working their way through the old personnel, while MI5 has quietly scrubbed the victims, and the entirety of the existing Slough House from its records.

River is still dealing with David’s death when Olivia Cooke’s Sid Baker turns up alive, having been presumed dead since Season 1. Then Hugo Weaving’s Frank Harkness, River’s estranged father and the former CIA operative turned mercenary who caused such havoc in Season 4, also resurfaces, while Diana Taverner (Kristin Scott Thomas), now First Desk at MI5, also finds herself tangled in the fallout. The further River digs, the clearer it becomes that the killings reach into the upper levels of the service, leaving Lamb and his Slow Horses to figure out why someone has suddenly decided that MI5’s discarded agents need to be permanently discarded.

Lowden suffers almost every indignity Slow Horses can plausibly inflict on a human being, while still having to maintain the illusion that River could one day become a properly functioning intelligence officer. River is grieving David, getting chased, shot at and thrown into increasingly stupid physical predicaments, all while finding himself re-smitten with a resurrected old flame; yet Lowden keeps enough composure in his performance to remind you why people keep calling him the next potential James Bond. He certainly has the rumpled poise and physicality for 007. But if he actually does bag the role of cinema’s most iconic spy after playing television’s worst, that will be an extraordinary piece of casting history.

Oldman has now inhabited Jackson Lamb for so long that the character’s slouch and spectacular contempt for personal hygiene have become as recognisable as his snide barbs.