BBC One’s sexy new drama, Wanderlust, starring Toni Collette and Steven Mackintosh kicked off tonight with a cracking first episode, which quietly pushes the envelope of what’s done on the channel…

At this point it’s a genuine privilege to see Toni Collette do what she does best. The Australian actor may currently be soaring on the back of her barnstorming performance in the deliciously grim Hereditary but that’s just one in a long line of terrific showings, and her presence here is a tremendous boon.

Jumping from an internationally acclaimed horror movie that has her possibly tipped for an Oscar nomination to a gentle BBC drama may not be the most obvious career move, but Collette is clearly drawn to projects that interest her – and that’s a tremendous compliment to Wanderlust. It’s easily clear why Collette signed up for the series because characters like Joy Richards – a committed family woman in crisis – are what she excels at.

Wanderlust starts off with the classic conceit of a married couple coming to terms with the fact the fire has gone out in their relationship. The series doesn’t exactly modernise it – open relationships are practically old hat at this point – but there’s something refreshing about how writer Nick Payne, based on his 2010 play of the same name, tackles sex here.

There’s no beating about the bush, so to speak, as Payne and director Luke Snellin are open about Wanderlust’s mission statement of highlighting variety in middle-aged sex lives. Words like ‘raunchy’ and ‘erotic’ have been tossed around in early publicity, which is, of course, ludicrous because Payne hasn’t crafted some BDSM thriller. If anything, Wanderlust is wholesome: everything shown is sweet, alimentary and consensual. It’s about sating middle-aged desire and exploring new avenues in life, not Lady Chatterley’s Lover.

What’s interesting for a six-part series is that Wanderlust blazes through a not-insignificant amount of plot for its opening episode. There’s quite a large ensemble here – we’ve got Alan and Joy as our core couple; then Tom and his relationships with girls at school; Rita and Neil, the unhappily married pair next door; and Joy and Alan’s new loves, Marvin and Claire. That’s all without mentioning Naomi, the Richards’ daughter who returns home early from her gap year after a bitter break-up with her girlfriend.

Wanderlust may advance through a lot of plot but it still feels like there’s a lot of places for the series to go because you want to spend time with these characters. At times it might edge into fairly cliché territory – the school-set scenes with young Tom felt plucked from Waterloo Road – but there’s a warmth in Payne’s script and in the performances that keep you invested.

While Collette is, naturally, the stand-out, Wanderlust is very much an ensemble piece. Steven Mackintosh does some fine work as Alan, and it’s difficult to make a homebody like him endearing but the nuances in Mackintosh’s performances really bring him to life and have you understanding where Alan comes from. He’s a different man when he’s with Claire and an open relationship might do him the world of good.

Speaking of Claire, Zawe Ashton is a reliably strong performer so it’s great to have her back on our screens again. She’s perfect for the role, delivering many of the premiere’s funniest lines (the plane proposal anecdote was a delight) and never forcing Claire into Manic Pixie Dream Girl territory, which a character like that could easily enter.

Wanderlust is remarkably gentle for its apparently revolutionary approach to sex and while its approach to middle-aged sexuality is admirable, it’s a terrific, old-fashioned BBC drama at heart. Bagging someone like Toni Collette is a great coup and she works wonders with the material but she’s aided by the generally excellent cast and Nick Payne’s empathetic script. More, please.

Wanderlust continues next Tuesday on BBC One at 9pm.