Porridge originated from an idea used in a 1973 series, in which Barker starred, called
Seven of One. Each of its seven 30-minute episodes saw him playing a new character in a different setting.
In the second instalment, "Prisoner
and Escort", a prisoner called Fletcher (played by Barker) was being escorted from London to Slade prison by warder Mr Barrowclough
(Brian Wilde).
After a long train journey,
Fletch asks to relieve himself at the tiny station where the prison minibus is waiting to take them to the prison. He relieves
himself into the petrol tank, and when the van stops in the middle of the moors, Mackay strides off to the prison for help.
Fletch encourages Barrowclough to spend the night in an abandoned cottage. Here, Fletch escapes and spends the night running
around the moors. He eventually discovers a second empty property and hides within it. Fletch finds that he is not alone,
and prepares to attack his companion. Only then does it become obvious that the other resident is Barrowclough, and that the
cottage is indeed the same one from which he had set off. Back at the prison, Mackay tells Fletch that the petrol tank was
fuller that when last checked, and that it was 'definitely not 5-star'. Thus started the humorous conflict between Mackay
and Fletch.
A year later,
when the BBC were looking for a premise for a sitcom in which Barker could star, this episode was chosen. (The first Seven
of One programme was also developed into a series: Open All Hours.) The central character of Porridge is Norman Stanley Fletcher, described
by his sentencing judge (whose voice was also provided by Ronnie Barker) as "an habitual criminal". Fletch's cellmate is Lennie
Godber, a naïve inmate serving his first prison sentence, whom Fletch takes under his wing. Mr Mackay is a tough warder whose
bark often turns out to be worse than his bite, and with whom Fletch often comes into conflict. Mackay's subordinate, Mr Barrowclough,
is more sympathetic and timid — and therefore prone to manipulation by his charges.