I like to imagine Julia Davis and Jessica Hynes, who co-wrote and co-star in Lizzie and Sarah (BBC2, Saturday), sitting down together to create it. Hell, it must have been fun.

"We can't get away with that, can we Jessica?"

"Oh go on Julia. So Michael will put a pillow over my head so he doesn't have to look at me when we're having sex. And I'll almost suffocate. Then, when he's done his business, I'll say thank you, really meekly, trying to hide my tears."

"Ha ha ha, brilliant. And my husband John can have sex with the obese Brazilian au pair - pumping away loudly, enthusiastically and frequently, all over the house and in full view of everyone. I'll clear up after them, pretend it's not happening, play Boggle and make toasties . . . "

We know about Julia Davis's inappropriateness from the wonderful Nighty Night. But here, with her new partner in crime, she's cranked things up - or plumbed new depths - to a whole new level of excruciating. Ouch, it's painful - it has you wincing and squirming, clenching and screaming inside. Then exploding with laughter. Because it is very, very funny.

It's not just about shocking, though, and getting away with things (an awful lot of things, it must be said - 11.45pm is really the only time this could possibly have gone out). Lizzie and Sarah is also beautifully observed. It is far-fetched, but not that far-fetched. This is not a million miles away from stuff that goes on in pretty much every family (infidelity, ageing, insensitivity, cruelty, Boggle). And it's this - the recognition and familiarity - that makes it both so painful and so funny. In fact, when Lizzie and Sarah stop being walked all over, go postal and start to take revenge with a gun, it becomes less successful, I think. Because suddenly it's less believable. Still funny, just not so painfully so.

Anyway, it's a treat - brave and hilarious. With brilliant performances, too, particularly from Jessica Hynes (who, along with Julia Davis, plays a 16-year-old as well as a 56-year-old). It would be criminal if this pilot wasn't turned into a series - though, with a large percentage of the characters now dead on the floor, there may be some logistical issues to sort out. No worries, Davis and Hynes can just get together and dream up some more. I'd like to meet anyone they come up with.

If it was too late and you missed it (maybe you were in bed with a pillow over your head), go and watch Lizzie and Sarah on iPlayer. And if you did see it, watch it again. You'll notice things you missed first time round, like the boobs drawn on the zeros in 2009 in the poster for Vicki's memorial concert. "Vicki Bobin, 'she fell asleep with angels', 1993-2009" (with boobs). Vicki was run over by her own pervy father, who was distracted by her friends in their netball kit. See what I mean about the inappropriateness?

Julia Davis is certainly no stranger to black comedy, having already appeared in twisted shows like Human Remains and Nighty Night, but it's a little surprising to see Spaced's Jessica Hynes (nee Stephenson) partnering her to write and star in a black-hearted tale of suburban revenge...

Lizzie (Davis) and Sarah (Hynes) are two fiftysomething housewives living in suburbia, both married to loathsome husbands who treat them with callous disregard and sneering contempt. Lizzie's husband John (David Cann) is having an obvious affair with their corpulent, lazy housekeeper Branita (Jessica Gunning); Sarah's husband Michael (Mark Heap) has taken to having meaningless, functional sex with her while he hides her face behind a pillow. Both introverted women are cowed into submission and have allowed themselves to accept their lot in life, as unloved slaves whose only escape from tedium and bullying is an amateur dramatics society. However, after a day of particularly unforgiveable treatment by their other halves, Lizzie and Sarah find themselves pushed to breaking point and, having come into possession of a handgun, decide to enact their revenge...

Lizzie And Sarah is of a particular style and content that many people just won't find particularly funny, that much is certain. Indeed, the BBC were allegedly so dumbfounded by this pilot's depressing tone that they scheduled it for a Saturday night graveyard slot of 11.55pm, so the chance of a full series doesn't look likely. If one is even necessary, as the story appeared to reach enough of a conclusion that I can't imagine what else Lizzie And Sarah would have to say. It was effectively 15-minutes of matrimonial bullying that segwayed into a domestic revenge scenario that lacked imagination because it was basically comprised of shooting their psychological aggressors dead with a gun they'd stolen from a thief.

The titular characters themselves were interchangeable; having no meaningful differences in temperament, accent, lifestyle, or taste in men. Their horrid husbands were likewise peas in a particularly odious pod. A subplot involving a memorial for a girl ran over by her own father's (Kevin Eldon) car, which inspired a musical memorial performed by two teenage classmates (Davis and Hynes), who gyrated to the Sugababes' Hey Sexy for the approval of a talent scout in the crowd, just felt misplaced and could have been cut entirely.

As a fan of Davis, Hynes and black comedy in general (which nobody does quite like us British), Lizzie And Sarah certainly had decent moments of chilling humour, uncomfortable bad taste, and jokes so near the knuckle they drew blood. However, a feeble storyline, near-identical characterisation for the leads, and unimaginative vengeance (just shoot the browbeaters), dealt enough blows to make this pilot feel like a wasted opportunity. I'd like to believe Davis and Hynes knew there'd be little hope of a full series, so opted to complete their story here, because I don't see any reason or need for more.

Written by Julia Davis and Jessica Hynes, this new pilot has been scheduled in a spectacularly awful slot by the BBC, but it's well worth setting the recorder for, since it takes a shot at everything comedy is supposed to be and blows it to bits. Lizzie (Davis) and Sarah (Hynes) are two middle-aged women trapped in mundane but cruel marriages, for whom it all unravels, slowly, and then very quickly. Everything Davis has a hand in comes with the obligatory "dark" tag but, even by her standards, this is exceptionally brutal. It's also brilliant. If the BBC do decide to commission a full series, they've got bigger balls than the Total Wipeout assault course.

Lizzie and Sarah preview

Producer Ali McPhail says: "As a producer you want to make a great show a lot of people will enjoy. I believe we've made a great show in Lizzie and Sarah, written by and starring the brilliant Julia Davis and Jessica Hynes."

The 'Lizzie & Sarah' iPlayer Challenge

We at The Velvet Onion love an underdog, and Lizzie & Sarah is no exception. The new pilot from Julia Davis & Jessica Hynes has been buried in a graveyard slot this evening, and its been up to friends of the pair (including Edgar Wright, Simon Pegg and our own Noel Fielding and Dave Brown) to plug the show for them!

Has the BBC lost its nerve over this dark comedy?

You loved Julia Davis in Nighty Night. You loved Jessica Hynes in Spaced. So why is their new pilot on at 11.45pm?

Julia Davis (Nighty Night, Human Remains) and Jessica Hynes (Spaced, The Royle Family) have partnered for the new BBC2 comedy pilot Lizzie And Sarah, playing two fiftysomething suburban housewives who are ignored by their selfish husbands, but are inspired by the tragic death of a teenager to take revenge.

If you're a fan of very dark comedy, this looks promising, although the "joke" of the trailer appears to the total absence of any traditional laughs and its oppressive, sinister tone. But it's packed full of familiar faces from British comedy (Mark Heap, Kevin Eldon, David Cann, etc), most of whom have appeared in similarly blackhearted comedies; from the aforementioned Nighty Night and Human Remains, through satirist Chris Morris' Brass Eye and Jam.

Apparently, Lizzie & Sarah is being sneaked out on BBC2 with little fanfare and in a graveyard slot (Saturdays, 11:45pm!) because the BBC were shocked by how dark and twisted it is, which is a shame. But I know that fact just gave plenty of people a frisson of excitement. Lizzie & Sarah hits the airwaves on 20 March. I hope it's funny, but in a sick way.

Human Remains: a macabre comedy masterpiece

Rob Brydon and Julia Davis may have gone on to bigger things, but this six-part black comedy remains their finest hour.