Aged lovebirds Celia and Alan (Anne Reid and Derek Jacobi) potter happily through their new life together as their families fall apart around them. Celia's brittle daughter Caroline (Sarah Lancashire) rages against the infuriating and inept drunken man of straw she married, while Alan's daughter Gillian (Nicola Walker) is humiliated by that nasty piece of work she's sleeping with.

This all sounds desperately soapy, but it isn't, though things get a bit weird by the end with some nonsense about a haunted country house that feels like it belongs in another drama altogether.

Still, writer Sally Wainwright likes to spring surprises (and there are quite a few of those in this episode) as Alan and Celia take the next step in their relationship. Caroline, meanwhile, drops her guard in that lovely big house in Harrogate so we glimpse the well of loneliness that lies beneath her flinty exterior.

Anne Reid as newly betrothed Celia has such a quiet-killer way of delivering a line; when her spineless twerp of a son-in-law gleefully explains the torrid sexual relationships in his latest book she fells him with, "Oh well, there we go." She might as well have shot him with a bow and arrow. Celia later explains to her fiancé, Alan: "He writes novels... they're nowt."

As Sally Wainwright's flinty romantic drama picks up pace, Celia and Alan (Derek Jacobi), reunited after 60 years, are planning an engagement party. Their respective families are still angry and baffled that the pair so suddenly decided to marry. Celia's unhappy daughter, who recently dabbled with lesbianism and who even more recently took back into her home the adulterous, novel-writing spineless twerp (the brilliant Tony Gardner), is particularly furious. But Celia and Alan don't care, they are too busy buying a sports car.

Celia (Anne Reid, mumsy with a hint of steel) and Alan (Derek Jacobi, twinkly with a hint of melancholy) are unbowed by the uniform opposition of their families to their engagement. In fact, while their children's private lives crumble (affairs, betrayals, midlife crises), their own bond looks stronger than ever. But could an engagement party reopen old wounds? As a portrayal of old age, it's not exactly 'Amour': the narrative signposting is constant and occasionally distracting. But what could have been whimsical - bordering on twee - is lent integrity by Sally Wainwright's characterisation, dignity by Reid and Jacobi, and drive by the goings-on among the excellent supporting cast, with professional scene-stealer Tony Gardner's oleaginous cheat as the stand-out.

Video: Writersroom interviews... Sally Wainwright

BBC writersroom interviews TV writer and playwright, Sally Wainwright (Last Tango in Halifax, Scott & Bailey, At Home with the Braithwaites).

Sally tells why she's always had a compulsion to tell stories, how Coronation Street influenced her writing and how she found her voice as a writer.

She talks to us about why self-editing is so essential and why it's so important to get the details right.

Celia and Alan's touching whirlwind romance has been 60 years in the making. After dropping the bombshell on their children at the end of last week's episode that they're getting married, the newly engaged couple - played by Anne Reid and Derek Jacobi - have some exciting plans to make.

Not to mention bridges to build between their daughters Caroline and Gillian, who didn't get off on the right foot. "Trailer trash" and "b****" isn't the best way to greet your prospective in-laws.

So Alan and Celia decide to throw a little ­engagement party, which, as things turn out, should at least take the heat off their romance and stop it from being the sole topic of chat for a while.

This wonderfully bittersweet comedy drama from Sally Wainwright about love among the over 70s ticks all the right boxes thanks to sympathetic writing and excellent performances with depth.

Underneath Celia's twinkling optimism and girlish delight there lies a lifetime of experience and, when she puts a patronising young salesman firmly back in his box tonight, we can see exactly where her daughter Caroline (Sarah Lancashire) gets her take-no-c**p attitude from.

One scene tonight where Caroline cuts a meddling colleague down to size makes you want to stand and cheer.

Caroline's estranged husband John (played by Tony Gardner, who also plays Professor Shales in Fresh Meat) is back in the family home, but the appearance of his other woman (Ronni Ancona) is about to rock that little boat, too.

Despite its charm it was difficult to see how Sally Wainwright's romantic comedy could sustain itself for another five episodes after ageing Yorkshire love-birds Alan (Derek Jacobi) and Celia (Anne Reid) announced they were getting married last week. Fear not, though, this second part proves just as engaging as the back stories of the extended families led by their put-upon daughters, headmistress Caroline (Sarah Lancashire) and farmer Gillian (Nicola Walker), develop into an entertainingly fraught family saga.

I wasn't looking forward to Last Tango In Halifax. It's a ­cliché for TV dramas or films to nick and amend famous titles, and the results are invariably disappointing (viz Once Upon A Time In The Midlands). But Sally Wainwright's wrinklies' romcom is a sweet thing. Sixty years previously, a budding schooldays romance fizzled out when, connivingly, a note wasn't passed on. The protagonists' marriages to others ended through death and deceit, and now social media has put them back in touch.

"Dear Celia, I'm planning a trip to Skipton next week, possibly Monday..." types Alan into his laptop, as if he's still at his bureau with a pad of Basildon Bond. The drama benefits greatly from its West Yorkshire locations but the buildings don't dominate; I just happen to like the dark satanic stonework. It benefits even more from the performances of Derek Jacobi (best known for In The Night Garden's Iggle­piggle - sorry, that's just in our house; I mean I, Claudius) and Anne Reid.

She's hilarious. "What do you suppose a crappuccino is these days?" she wonders. "Still, if you're not taking risks you're not living. That's what our William says, and he never leaves his bedroom." By the end of the first episode the codgers had decided to get married. With their highly dysfunctional clans now being forced together - Tony Gard­ner specialises in prats (see also Fresh Meat) - there's obvious potential here, but for me Last Tango could have ended with that announcement.

Wainwright pens authentic dialogue sprinkled with salt, as her Scott & Bailey proves.

Radio Times review

The first episode of Last Tango in Halifax (Tuesdays BBC1) was perfect, such that I don't think I want to watch another one - or if I do, I'll pretend it's a different programme and this was a precious one-off. Anne Reid and Derek Jacobi were two Yorkshire pensioners, both widowed, who had been separated by chance as teenagers but still lived not too far apart. Pushed onto Facebook by the grandkids, they found each other, met in person, and slowly revealed that each had pined for the other for 50 years or more.

Reid and Jacobi unfurled the fantasy I-love-you-too romance in Sally Wainwright's sparky script until the last scene, when their families burst into the café with their subplots about ex-husbands and tricky children and lesbian affairs and mysterious pasts. There's five more episodes of that stuff, but anything that isn't those two impeccable actors glowing at each other across a teapot will be a cold second-best.

Last Tango in Halifax, BBC One, review

The ways in which this story of late love might have gone wrong were numerous, but with the help of beautifully nuanced performances from her cast, Sally Wainwright steered an entertaining course between the Scylla of sentimental regret and the Charybdis of patronising caricature.

Last Tango in Halifax, BBC One

Bertolucci meets Alan Bennett in Sally Wainwright's gentle generation game.