Nick Payne's outstanding BBC drama Wanderlust hasn't been light on visual metaphors. Last week we rolled our eyes knowingly as Joy (Toni Collette) literally got back on her bike for the first time following her road accent. She went on to have pleasurable sex for the first time since the collision (with a man who wasn't her husband) and suggest that she might want to have an open relationship.

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In episode two, we got to watch Joy diving into the deep end of her local swimming pool (she goes there for hydrotherapy classes and inadvertently finding attractive single men). It took a moment for Joy to throw herself off the edge, and it looked at one point as though she'd chicken out. But then she did it – launching herself with carefree abandon into a perfect dive. Simultaneously, she and her husband Alan (Steven Mackintosh) decided to do this whole 'open marriage' thing and tell their respective new sex-partners about their plans. Can you see what we mean about visual metaphors?

In the end, the execution of the dive went a little better than the plans for the open relationship. In a brilliantly clever bit of writing that really taps into the perverse, contradictory nature of the human spirit, Alan and Joy found themselves closer than ever by describing (in erotic detail) what, exactly, they got up to on their nights away from one another. Unfortunately, their new lovers didn't take the news that Joy and Alan were going to stay married quite so well.

The struggles of sex and sexual desire are sensitively and evocatively approached in Wanderlust. Just as Alan and Joy are moving their marriage into unknown waters, so their children are discovering masturbation, heartache and sex for the first time. All with excellent humour and the inter-tangling of lives that lead to juicy cliffhangers.

Perhaps next week we'll see Joy literally hitting a brick wall, or smashing through a glass ceiling, or shooting herself in the foot. The possible metaphors are endless.

Wanderlust episode three airs Tuesday 18 September