With The Liver Birds, the successful massively sitcom about two Liverpudlian girls sharing a flat, Carla honed her comedy craft, bringing strong women characters to a male-dominated medium and finding brilliantly observed moments of pathos and humour in the day-to-day trials and tribulations of her characters.
After ten series, Carla was ready to try something different and, certainly, Butterflies has an unusual set-up for a comedy. The show is essentially about an ordinary suburban housewife (Ria played by the sublime Wendy Craig) deciding whether to have an affair. Not because her husband is nasty or violent or vicious, but just because he's... well, just a bit dull.
Sitcom veteran Geoffrey Palmer plays Ria's straight-laced, traditionally--minded husband, Ben. He's a reserved sort of chap who works as a dentist and is also an amateur butterfly collector. He's given Ria a comfortable life but the last word you'd use to describe him is 'fun'.
The couple have been married for 19 years and live in a pleasant Cheltenham neighbourhood with their two boys - older son Russell (Andrew Hall) and the younger, Adam, played by Nicholas Lyndhurst, who surely needs no introduction. The pair have the expected teenage scrapes and the odd minor crisis but nothing irresolvable. There's inevitable friction but the family essentially all get along. So, with such an agreeable if unremarkable existence, why does Ria have such an overwhelming desire to run for the hills?
Temptation comes in the form of Leonard (Bruce Montague), a seemingly successful businessman, recently separated from his wife. The pair strike up an unusual friendship and, whilst Leonard is undoubtedly something of a soulmate, is he really worth chucking away a marriage and family for?
Ria's search for 'something more' and the 'will they-won't they' relationship with Leonard forms something of an existential journey at the core of Butterflies - pretty remarkable stuff to have in a sitcom that also manages to be consistently funny, with laughs coming from more conventional and expected sources alongside the unusually bittersweet moments.
Carla was a writer who could truly bring the extraordinary out of the ordinary, and Butterflies showcases these skills brilliantly in what is, undoubtedly, one of the landmark UK sitcoms of the 1970s.