If you've missed the cringe comedy David Mitchell and Robert Webb made famous with British shows like Peep Show and That Mitchell and Webb Look, there's good news: The comedy duo has reunited for Back, a six-episode British import, the first episode of which airs tonight on Sundance Now.

The lads have aged, and they're using that: The series is powered by middle-aged disillusionment. Mitchell plays Stephen, a 40-something alcoholic trying to live up to his dead father's legacy as a publican in the tiny town of Stroud. Having failed at marriage and the law, he's trying to usher his dad's pub, the John Barleycorn, through a successful transition. Webb plays Andrew, Stephen's sometime foster brother and an urbane and charismatic cosmopolite. He's returned "home" to pay his respects to his deceased foster father — and, Stephen suspects — to take over and ruin his life.

It's a great premise: nasty sibling rivalry with the frisson of a silly but engaging psychological thriller. Back departs significantly from Peep Show (which occupied Mitchell and Webb's points of view equally) in that you're mostly restricted to Stephen's feverish, paranoid perspective as his humble dream of running an authentic English pub recedes, crushed by Andrew's superior competence. Andrew — who initially presents as something of a sociopath — starts off as a cipher and only gets harder to read, to the point where the viewer genuinely can't tell whether Stephen's manic conviction that Andrew is evil is correct or a divorced alcoholic's spiral towards rock bottom.

If that brand of bleak humor sounds familiar, it's because Back was written by Simon Blackwell, whose grimly hilarious credentials include Veep and The Thick of It. He's chosen a less explicitly political setting this time; Back is set in a tiny town in rural England in danger of becoming a Disneyfied version of itself: "We really liked the idea of something being authentic and its authenticity being trumped by something that's inauthentic but which looks authentic," he told me. "I live in the part of the U.K. called the Cotswolds where a lot of traditional country pubs have been bought and remodeled to look like they're traditional country pubs and more people visit them because that's what they think a traditional country pub should look like."

Authenticity is Back's animating concern. If the series deals at one level with unexpectedly serious universal subjects like death and marriage and treacherous childhood memories, its more comical side is specific and rooted in a very particular time. "Over here at the moment, Brexit colors everything," Blackwell told me. "It's the background music to everything, the same way as the 45th president is the background music to everything I think that's happening in the U.S. at the moment." The struggle over what "authentic Britishness" means maps onto the rivalry between these technical "brothers": It's "the idea of people who want to move like Andrew, around Europe, as citizens of everywhere, and people like Stephen who stay in one place and regard themselves as citizens of that town," Blackwell says.

The irony — as Blackwell points out — is that the parochial Stephens who want to stay in their towns are the ones who voted "Leave," and the urban nomads like Andrew voted "Remain." These are confusing times, and Back capitalizes on that confusion by making the basic question of the series — is Andrew the devil or is he a normal guy? — basically unanswerable. There's no stable ground here and no conclusion; ambiguity, not plot, is the point.

What grounds the series, then, is Mitchell and Webb's comic timing. They've been working together for so long — almost two decades — that they evoke an instant world onscreen. If Mitchell's character in Back is duller and less articulate than Peep Show's Mark Corrigan — and Webb's Andrew is exponentially smarter than Jez — that doesn't alter their basic dynamic. Webb longs for Mitchell's inherited advantages; Mitchell stews resentfully at Webb's corrupt and charming ease.

Back isn't ambitious; a friend described it as a comedy that put on a fake mustache to pass as a rural English crime drama. It's quick and funny and boasts a stellar supporting cast — Jessica Gunn does a star turn as Jan, Stephen's overly sympathetic waitress; Louise Brealey quavers and hopes as Stephen's artist sister Cass; Pennie Downie shines as his amiably vacant mom; and Olivia Poulet manages to steal a scene or two from Mitchell as Alison, his character's ex-wife. There's plenty, in other words, with which the series to wander and expand.

"If there was an oath a writer had to take, the first thing you would have to say is I will not bore people," Blackwell told me. "That would be at the top of the list." But the show's subtext is as clear as its aspirations are humble: If Peep Show sometimes skewered Blair-era fantasies about what a cosmopolitan United Kingdom could be, Back takes a dull and slightly depressive scalpel to Britain in the age of Brexit.