Sitting on a toilet, frowning, Freya (Kyla Harris), a thirtysomething artist and wheelchair user, is having trouble with her bowels. Donning a blue glove and lubricating her finger, Jo (Elena Saurel), Freya’s estranged best friend and new personal assistant, offers to lend a hand. Within seconds, she is bent over, attempting to stifle a bile reflux. “Are you gagging?” asks Freya, mortified. “This is so humiliating!” Bending over in apology, Jo gamely pulls down her pants. “Put your finger in my ass!” she cries. “For equality’s sake!”

I don’t know if this is the first time anal stimulation for constipation has been broadcast on British television, but then I don’t suppose anyone has been keeping a record. That this is a scene in the BBC’s newest disabled-led comedy, rather than a particularly rough episode of Casualty, makes it what a press release might describe as “groundbreaking”. I would call it very funny.

We Might Regret This is the brainchild of Harris and Lee Getty – real-life friends who, on and off over a decade, worked together as care-user and PA. Inspired by their experience, but with a large dose of fiction, the series sees Harris’s Freya move from her native Canada to London to live with her long-distance partner, Abe (Darren Boyd), a strait-laced bankruptcy lawyer “in the middle of a midlife crisis, albeit a very inclusive one”.

When Freya finds herself without care and sofa-surfing Jo finds herself without a home or a job, she moves in with the couple and becomes Freya’s 24/7 PA – and Abe’s 24/7 headache. The premise is simple, but novel: what would it be like to hire your best friend to help you wash, move and go out? Or, as Jo puts it: “What happens when the person you love starts paying you to stay around?”

Harris and Saurel’s partnership has an effortless intimacy that is a joy to watch, but the series’ strength is its ensemble cast. There is Abe’s soon-to-be ex-wife, Jane (played with fantastic dryness by Sally Phillips), and his wayward son, Levi (Edward Bluemel), who is busy trying to get into bed with Jo. Some of the funniest early scenes come from Freya’s outgoing PA, Ty (Aasiya Shah), who plays “well-meaning but useless” with aplomb. Part of the humour comes from the way their relationship subverts how we are often told to treat disability and care. Freya isn’t a helpless figure portrayed as lucky to have a carer. She is an adult in control who is increasingly exasperated by her employee (“She’s going to make me commit a crime”).

It feels like a fully rounded universe after the first episode, with all the main players and their various hangers-on in place within 29 minutes. Even the secondary cast, such as the two Olivias, who enthusiastically scout Freya as a “diverse” model, slot in with ease.

While the leads are relative newcomers, a range of brilliant cameos means the show feels like a who’s who of modern British comedy, from Home’s Youssef Kerkour, as a builder pricing up adaptations for Freya’s new house, to This Time With Alan Partridge’s Tim Key, as a bigoted restaurant owner going bust. The standout, though, is Ghosts’ Lolly Adefope, who pops up in episode two as a former soldier now running Jo’s unhinged PA-training workshop. “Don’t ask me what I did, don’t ask me for dates,” she tells the group. “Whether you’re out there in the field or here entering data, it’s all military.”

There has been a flurry of “issue-driven” comedies lately, from This Way Up to Feel Good. On paper, WMRT is part of this trend. But that would fail to do it justice. Yes, this is a trailblazing portrayal of a disabled woman on screen, but it isn’t really about disability or care-giving. It’s about relationships – messy, complicated, co-dependent. The truth at the heart of the series is made clear: Jo needs Freya as much as Freya needs Jo.

All six episodes were available to preview, which suggests that the BBC is confident about the end result. It should be. The script has a wonderful pace, with witty one-liners and painful moments given equal space. There is a realism to the whole thing that feels liberating. As the chaotic Jo, Saurel brings an irreverence mixed with a vulnerability that makes me want to see what she will do next. Harris makes Freya feel like a character we have never seen on screen before, whether she is using a catheter in an alleyway because a venue has no accessible toilet or being interrupted mid-sex by her PA. You find yourself wondering how it took commissioners quite so long.