New comedy Sally4Ever is Julia Davis at her filthily funny best.

With Nighty Night, Hunderby, Camping and more, Julia Davis has a track record for creating comedy that’s just as horrifying as it is hilarious. Her own unique brand of TV where it isn’t unusual to find yourself giggling uncontrollably at what’s happening on screen while simultaneously hiding behind your hands. And she’s managed to do it again with her new series Sally4Ever, a co-production between Sky Atlantic and HBO.

It opens with the titular Sally (Catherine Shepherd) watching David (Alex Macqueen), her boyfriend of ten years, sing George Michael’s Faith as part of an acapella group. She’s visibly repulsed by him and we can’t blame her. At home, when David isn’t noisily slurping tea, picking his teeth and massaging ointment into his feet, he’s tearfully begging Sally to marry him. Eventually, perhaps influenced by reminders from her mum that she’s only got “a limited number of eggs”, Sally gives in and says yes. After all, as David tells her through pitiful sobs, “You’re not getting any younger, you’re not going to meet anyone else”.

He couldn’t be more wrong though, because Sally does meet someone else, and a chance encounter on the tube leads to a whirlwind affair with the enigmatic Emma (Julia Davis). However, Emma soon turns out to be a sociopath – which shouldn’t come as too much of a surprise if you’re familiar with Davis’ work – and wastes no time moving into Sally’s house, getting her fiancé out of the picture and telling her conservative parents that their daughter is gay.

Sally’s clearly in way over her head with her new love, but going back to her stale relationship with David, a man who comes over for supper and brings his own sausages with him, doesn’t seem like an appealing alternative. Could a happy medium present itself in the form of work colleague Nigel, played by Davis’ real-life husband Julian Barratt, who appears to have a bit of a crush on Sally?

Among the supporting cast at Sally’s workplace, which feels like the world’s least glamorous advertising agency, are Steve Oram as the office pervert and Felicity Montagu as a peculiar co-worker who labels her dairy products and was once run over by her own mum (“She said she thought it was a large dog, but we think she knew”). There’s also a brief appearance from Jamie Demetriou in the opening episode, with appearances from Vicki Pepperdine, Mark Gatiss and Sean Bean coming up.

While Davis’ last series, Camping, was a gradual build towards chaos in its finale, it doesn’t take long for Sally4Ever to reach this level of mayhem. In the opening episode alone, there’s a graphic, mind-boggling sex montage set to T’Pau’s China In Your Hand, which you’ll never be able to hear the same way again… On the basis of just the first two episodes, this might be Davis’ most boundary-pushing show yet, so who knows what horrors and delights she has in store for us in the rest of the seven-part series.