Having emerged as a writer of feisty, young working-class women with The Liver Birds, Carla Lane moved into more mature and middle class territory with Butterflies.
Marriage, family and the effect they can have on a woman's life were the central themes to this popular show, which ran between 1978 and 1983.
Ria is a housewife and mother, taken for granted by her family, who has regular - but chaste - assignations with Leonard: a wealthy man who offers escape from the drudgery into which she has fallen.
There is a dreamy quality to Ria, her mid-life crisis, though guilt-inducing, allows her to revel in what might be (but only ever in her head).
Wendy Craig was perfectly cast: Ria is just as easy to empathise with as she is to laugh at, her misty-eyed yearning and wistful demeanour make for one of the most triumphant yet forlorn central characters in sitcom history.
Geoffrey Palmer, after years of stalwart supporting performances in almost every TV programme imaginable, finally got the chance to play the joint lead, and is very funny as Ria's husband Ben.
A dentist by trade, Ben's butterfly collecting provides the show's title and central metaphor: should Ria spread her wings and fly?
Her bickering sons were played by a young man called Nicholas Lyndhurst, of whom we went on to hear more, and Andrew Hall, whose charm and affably cheeky comic touch unfortunately didn't give him the high profile his screen brother subsequently enjoyed, which just goes to show how fickle TV can be.
Leonard is everything Ben is not: extremely wealthy, interested in Ria, and very patient with her inability to commit, it has to be said. And yet is never quite enough to tempt her from her duty.
However, her dalliance with him seems to give her some form of inner peace, the series suggesting that happiness can perhaps reside inside one's own imagination and aspirations, rather than the more obvious shortcomings of reality.
Traditional sitcom dynamics feature in abundance: Ria is an appalling cook, Ben is prone to droll bon mots (if you've got Palmer, flaunt him) and the teenage boys argue and fight.
Beneath all this though, is a touching dissertation about reality and fantasy in which voiceover and dream sequences - not usual for a BBC sitcom by any means - are used to great effect. Some of the tougher aspects of life like teenage pregnancy and suicide are dealt with, but from the stoical point of view of a devoted mother and without sentimentality.
When it aired, Butterflies consistently topped BBC TWO's Most Watched programmes list, and the series spawned an ill-fated American version, which failed to capture the essence of the original.
It was deemed well established enough in the nation's consciousness to be granted a 10-minute special sketch as part of 2001's BBC Children In Need night, with Ria having just celebrated her 60th birthday and finding that very little has changed.
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