When we first meet Jackson Lamb (Gary Oldman) in Slow Horses, the camera has glided over the debris on his desk to find him waking himself up with a fart on the couch in his office. It’s a fitting introduction for an unlikely protagonist: Across Slow Horses we see Lamb routinely berate, belittle, and besmirch all those around him. He is TV’s biggest asshole, as unrepentant as he is vulgar. He is, also, a perfectly beguiling shitbag, and one of TV’s best.

The art of creating the perfect asshole might not seem complicated on paper. Evil, as the adage goes, is a constant, and often a childish one at that. It’s easy to imagine badness and carry it out on screen, however unskillfully. But Jackson Lamb is not simply a bad boss, or even a bad person. Slow Horses, adapted from Mick Herron’s Slough House series of spy novels, is always very careful about that, even when he’s just said one of the rudest things you’ve ever heard, whether it’s poking fun at someone’s addiction, mocking their dead spouse, or endlessly encouraging his employees to quit.

Oldman plays Lamb like a true pain in the ass — which is to say, aggravating and limiting, but decidedly sharp and constantly trying to communicate something deeper. It’s what makes him so profoundly frustrating to those around him: You can discount him at your own peril. But you’ll have to sit through a steady stream of causticity to find a pearl of wisdom.

Still, the writers of Slow Horses are careful to balance Lamb’s dickish behavior as best they can. That doesn’t involve tempering it so much as it is giving him a strange, acidic logic. He will frequently offer Standish (Saskia Reeves), who’s years in recovery from alcohol addiction, a drink. Showrunner Will Smith (not that one) says this is his own way of checking that she’s still on the wagon. (“It’s not the traditional way of checking that somebody is handling sobriety,” Smith laughs.) Even the smallest joke or fart is there to push people’s buttons, test a reaction, throw someone off the scent, or purely (as is often the case with those at the Park) demonstrating that he knows more than them. In all these times he is playing to expectations of him and his slobbish behavior, even when he’s simply out to subvert it.

“Lamb is all about minimal effort. He just wants to be behind the desk,” Smith tells Polygon. “He’d never admit he was doing the honorable thing — even though he always does. He saves the day; he always saves people. He steps up.”

But the final piece of the Lamb puzzle comes from a very important character choice: He’s not omnipotent, nor does his backstory excuse his behavior.

It’s straightforward enough as a concept. But too much of pop culture asks its protagonists to feel like good morals before they feel like good characters. Lamb is far from a gleaming beacon of virtue, but Slow Horses isn’t set up to make you think he should secretly be received as such either. He’s a jaded jerk, someone so wounded by betrayals in his past that he takes it out on those around him constantly. To Lamb, his abuse is a mercy, a way to discourage them from getting eaten up the way he was. After devoting his life to MI5 and trusting in his friend, what he has to show for it is a dirty conscience and a filthy mouth. He didn’t want to be a civilian, but he can’t bring himself to serve the institution either.

Like so many complicated protagonists — and, increasingly, villains — Lamb has good reason to be jaded. It’s a late reveal, pulling back on his central wound with what Smith remembers in a single line: Years ago, Lamb had to go and shoot his friend and mentor Charles Partner, and in return he asked for Slough House.

In a way, this guides many of the seasons of Slow Horses, which inevitably circle back in some way to how Lamb’s life was shattered by Partner’s betrayal. But the way we see it guide Lamb, mostly, is merely deeper into churlishness. Self-awareness is kept totally to himself. He uses his keen spy skills to learn things about people in order to weaponize them and throw them off their feet. Unlike many of those complicated villains (and their heroes), this is not so that we can better understand how he’s good, actually; Lamb’s arc is at its end, and the damage has been done.

Still, Slow Horses is smart enough to know that even smoking ruins yield treasures. Perhaps the greatest trick of Lamb’s competence is that he is still hard at work, even when he shrugs it off. He doesn’t know everything, he just knows enough. “We always feel he’s the smartest guy in the room, but once he’s got all the bits he’ll let the Slough Horses go off and do the leg work,” Smith says. “He doesn’t let people in when he’s ahead; he can’t be bothered to explain to people. So he’ll only let them in on the bits that are going to motivate them.”

In a different show, a weaker show, Lamb might become a dangerously perfect protagonist with this sort of skill profile. Instead, he’s the perfect cautionary tale; a completely unlikable guy you still love and would never want to work with; the ultimate asshole. Even four seasons in, Slow Horses feels like an exercise in character without letting tragic backstory become the defining feature. It’s what allows Oldman to plant gorgeous little moments of hope glimmering through all that muck: You can see the shifts when he happens on an unexpected crime scene, or indications that a member of his team is missing — hell, even Lamb’s profile is defined by Oldman slouching his body and pulling his head in to make his frame appear larger than he is. He shifts into the man he was, the man he still could be but has no desire to chase anymore. He can’t help it, any more than he can help being so broken in the uncaring world of espionage. Like Smith says, he’s always going to step out — even if he’d rather not have to take his feet off the desk.

Slow Horses season 4 premieres on Apple TV Plus on Sept. 4.