It may come as a surprise to anyone who has read Mick Herron’s peerless Slough House novels, but Slow Horses, Apple TV’s high-profile adaptation of the first book in the series, is not funny.

Instead, it takes Herron’s uproariously comic premise — that a group of misfit British spies, cast out of MI5 for misdemeanors exaggerated and accurate alike, have been reduced to grubbing about in a grim office on the periphery of the City of London — and plays it almost entirely straight.

Gone are the laugh-out-loud one-liners and endearingly witty pieces of throwaway badinage. Instead,...

It may come as a surprise to anyone who has read Mick Herron’s peerless Slough House novels, but Slow Horses, Apple TV’s high-profile adaptation of the first book in the series, is not funny.

Instead, it takes Herron’s uproariously comic premise — that a group of misfit British spies, cast out of MI5 for misdemeanors exaggerated and accurate alike, have been reduced to grubbing about in a grim office on the periphery of the City of London — and plays it almost entirely straight.

Gone are the laugh-out-loud one-liners and endearingly witty pieces of throwaway badinage. Instead, we have a big-budget spy thriller, polished and scripted to within an inch of its life. It’s a bit like seeing the Fresh Prince of Bel-Air reinvented as a gritty urban drama. But thankfully, it’s also terrific.

Herron’s central conceit is that the designated no-hopers and failures who have committed various sins are actually competent (and occasionally) brilliant agents who can excel where their superiors in their Regent’s Park headquarters cannot. And this is nowhere clearer than in the casting of the excellent Jack Lowden as the James Bond-esque River Cartwright, who has earned his own rustication for the spectacular bungling of a training exercise. In the book, it’s an opening set piece that wrongfoots the reader in elegant and witty style, setting up the reversals and twists that will ensue later. But here, thanks to the (presumably) huge budget that Apple has provided, we see Lowden’s Cartwright in full 007 mode at the airport, with a superbly tense and expansive action scene that sets out the series’ raison d’être: this is no time for laughter.

Thankfully, the show also has a particular trump card to play: the casting of the great Gary Oldman in the lead role of the grumpy, flatulent and generally socially regrettable spymaster Jackson Lamb, who sums up the men and women nominally in his charge as “M-I-fucking useless.”

In the novels, the gradual revelation of who and what Lamb is, and why he has been sequestered to Slough House, comes as a grippingly ornate drip-feed of sensational information, but the series has its own pithy shorthand. Anyone who remembers Oldman’s understated performance as George Smiley in the 2011 film adaptation of Tinker, Tailor, Soldier, Spy might be surprised to see how different he is in appearance and manner here; the most chameleonic of actors fully immerses himself in the role of an overweight, obscene figure, given to banging on ceilings to summon his inferiors and generally making their lives a misery. But if you want to convey intelligence and nuance, you cast Oldman, and you will not be disappointed. So it proves.

The main narrative revolves around the abduction of a Muslim student by a far-right British group called the “sons of Albion,” who seek to execute him live on camera in a deliberate quid pro quo for atrocities perpetuated by ISIS, but there are complications, and traitors. All of this is conveyed economically and thrillingly, thanks to a taut adaptation by British writer and comedian Will Smith and pacy direction by James Hawes. And fine supporting performances by Kristin Scott Thomas as “Lady” Diana Taverner, a high-up at Regent’s Park, Jonathan Pryce as River’s ex-service grandfather and Olivia Cooke as Sid Baker, a suspiciously competent-seeming Slow Horse, add intrigue and texture.

If I miss Herron’s laugh-out-loud humor and corrosive cynicism about the moral and procedural failings of those paid to protect us — who can even end up causing more damage in the process — than at least they have been replaced by the calm assurance of big-budget thriller television at its best. As we are subjected to the drip-feed release of an episode-a-week for the next month, a second series, based on the Dead Lions novel, is promised at some point in the future. On this evidence, it can hardly come quickly enough.