Although Steptoe and Son ran on British TV for twelve years it is one of those rare (maybe unique) examples of an idea which continued to develop and evolve rather than slide into stale repetition.
In its early years the series emphasised broad comedy. One well-remembered episode features Albert eating a meal while sitting in his bath, earning a rebuke from his son which became a national catchphrase: "You dirty old man!"
As time went by the characters became established and the writing began to emphasise the mutual dependency of two basically lonely men (Harold the batchelor and Albert the widower). Harold dreams of a better quality of life away from his father and constantly makes attempts to achieve something in his own right. His attempts are thwarted by his own lack of social standing and his father's scheming: if Harold joins a local theatre group, Albert joins too and becomes the star of the show.
Albert, for his part, fears losing his son and being abandoned in his old age. He will use any means (especially moral blackmail) to keep Harold at his side. More importantly he is far more realistic than Harold and sees that his attempts at social ambition are doomed.
The performances of Wilfrid Brambell and Harry H Corbett never faltered through the show's run. Galton and Simpson produced scripts of wit and insight and they performed with great skill and subtlety. This is a show where you laugh while recognising the truth and basic sadness of the situation in which the characters live.