Steptoe & Son was born from a one-off comic play, "The Offer" commissioned by the BBC in 1962 as part of Comedy Playhouse, a series of short plays all written by Galton and Simpson.
From the outset it broke the mould of British comedy. Where previous sitcoms relied on slapstick, gags and farce, Steptoe and Son introduced a note of gritty realism: its characters were resolutely working-class, down-at-heel rag-and-bone men scraping a living by spotting gems among other people's junk.
Father and son used earthy language and swore like troopers (at least as much as the BBC would allow them to) and both were given an added reality by being played by "straight" actors (Wilfrid Brambell and Harry H Corbett) rather than comedians.
Where other comedies revolved around interfering mothers-in-law and the sudden failure of the hero's braces the moment his boss came round, Steptoe's focus was on the inter-generational conflict that marked out the 60s.
While father Albert Steptoe was - as his son often reminded him - a "dirty old man", set in his grimy and grasping ways, 40-year-old son Harold was filled with social aspirations, not to say pretensions.
Many episodes saw Harold attempting to attract a posh "bird" (this was still the sixties and early seventies) with his literary erudition, love of classical music or amateur dramatic skills, only to have a single leer from his gargoyle-like dad put the kybosh on the whole affair.
Despite the advantage of Harold's relative youth, the audience always knew who was master in the Steptoe household. Albert, convinced his work in years (long) gone by entitled him to live off his son's hard graft, used every weapon from blood-curdling threats to pathetic wheedling to keep his son in line.
Over the years Harold's attempts to escape his dad became ever more desperate, even leading in one classic episode to him dividing the whole ramshackle Steptoe premises, right down to the TV screen, in two (the division of the TV resulted in failure when Albert realised the controls were on his side of the divide and a cackling Harold got his revenge by pulling out the plug on his own side).
Perhaps the best illustration of Harold's pathetic plight came in "The Desperate Hours" when, after the Steptoes were held hostage by two desperate prisoners on the run, Harold ended up begging the lead prisoner (a brilliant Leonard Rossiter) "Take me with you".
Steptoe and Son originally ran from 1962 to 1965 in black and white, returning in colour for four more series from 1970. So successful was it on its return that it was adapted for US TV as the much-loved Sanford and Son and spawned two film spin-offs.
Still regularly repeated, it remains as fresh today as it always was.