This may well be old news, but I have only just found the article in The Guardian ©2002 about how Gordon stumbled into being one of my favourite characters.
In 1981, Wharmby was one of five actors auditioned for a one-line part in the episode In The Service Of Humanity. The description of his role was simply "man on the roof". Another character was supposed to take away his ladder to rescue someone from the river. Wharmby's one line was: "Hey, bring back that ladder."
The way he tackled the part impressed director Alan Bell and writer Roy Clarke, the men responsible for ensuring the success of a series about the adventures of old men who had to be both sympathetic and interesting - not the easiest duality to bring off.
Bell, who found Wharmby "absolutely real", gave him another script, of the episode Car And Garter, to read aloud. Wharmby's reading was so convincing that Bell thought again about the casting of the episode, for which a well-known actor had tentatively been chosen; in the event, the role went to Wharmby.
At that time, he had done practically no acting; he kept on his day job as a painter and decorator for five years after his first appearance. Bell wanted to cast him on the spot, but, anxious about Wharmby's inexperience, invited him to other readings in London. It was soon obvious that whatever quality Wharmby had, it was not a flash in the pan.
He was also astute in knowing how to exploit a simplicity of manner. He once boasted to Bell that he was "absolutely confident" he could paint a house, including the paper on the ceilings, in two weeks. Whenever afterwards Bell asked him how confident he was - meaning about playing in the series - Wharmby deflected the question by affecting to think that it was only his skills as a house painter that were being questioned.