Have you been watching … Roger & Val Have Just Got In?

You wouldn't really expect people to get het up about Roger & Val Have Just Got In. It's not a show that trumpets its brilliance, or demands that viewers take notice of it. Quite the opposite: it's the tale of an average married couple, doing average married couple things in a 30s semi. But it's either one of the most captivating shows on television or a complete pile of unfunny tosh, depending on which side of the great Roger & Val divide one sits.

For me, it's the former. I love the show for all the reasons that other people can't get on with it: the lack of proper gags, a focus on the minutiae of relationships, the faceless spectre of Pam Bagnall. It might not be comedy as we know it, but Roger & Val manages to mix beautifully written dialogue with a quiet observational humour that can nevertheless leave the viewer gasping for air like Roger, on the stairs with a paper bag, shouting "Panic Attack!"

Much of this is down to the script. Writers Beth and Emma Kilcoyne (they are twins) manage to capture the essence of a relationship with astonishing affection, joy and empathy. There are elements that are universally recognisable – the gentle squabbles over dinner preparations, the bolstering of self worth, the instinct to protect your partner from hurt – but instead of slipping over into sitcom cliche, the conversations are so real, so unforced, that at times it feels like you're eavesdropping. Small things like Val's lamp obsession are done so beautifully, with such subtlety, that they underline the big moments as utterly, heartbreakingly perfect.

This darkness that lies beneath the couple's everyday chatter is the great strength of Roger & Val. (Or Val's everyday chatter, at any rate – Rog needs no excuse to embark on self-analysis). The second series has built on that terrible moment from the first, when we learnt that the couple's baby had died. Roger has a grownup son he's never known, and Val's faith in her husband is understandably shaken. The end of Wednesday night's episode – Val standing silently before the window, wrenched apart by her loss once more – was a brilliant piece of television.

I have never seen Dawn French perform better than she does here, in what is effectively, from an acting point of view, a straight role – Mrs Danvers costume aside. And she is more than matched by Alfred Molina as Roger, the complicated, leftwing botanist who adores her more than anything in the world. Watching them potter about their comfortable, cluttered house, ostensibly not doing much while really tackling enormous questions, I do sometimes have to remind myself that they are not actually a real couple, so in tune do they seem.

For some, Roger & Val is too stagey. And admittedly, it could be transplanted to stage with very few changes. The format, with events unfolding in real time and the pair never stepping outside; the dialogue; the conceit of a great supporting cast that we never see – these are all things that shouldn't really work on television, but somehow look fresh and new in these capable hands.

I wouldn't hesitate to call Roger & Val one of the best British dramas on screen – and French and Molina's performances as good as anything you'll see on TV this week. Whether or how funny the show is to me seems besides the point – it is absolutely essential TV. And I'm glad to report that next week's final instalment is an absolute cracker.