The first episode of Ronnie Barker's Comedy Playhouse-like Seven Of One introduced the northern shopkeeper Arkwright, who went on to become a firm TV favourite in Open All Hours. But the following week's edition, Prisoner And Escort, provided viewers with their first sight of the Londoner lag Norman Stanley Fletcher, who accrued an even greater popularity. Fletcher was a marvellous creation - a bona-fide TV comedy icon, one of an elite number that also includes Alf Garnett, the Steptoes, Basil Fawlty and Victor Meldrew - and Ronnie Barker, who by the mid-1970s was at the acme of his profession, was sensationally good in the role.

Following their Seven Of One pilot, the writers Clement and La Frenais waited, and waited, for the BBC to decide whether or not to develop the idea into a full series. So long was the wait that, in the meantime, they went to LWT and developed a variation on the comedy-crime theme, Thick As Thieves, which starred Bob Hoskins and John Thaw. When that folded after one season, the BBC were at last persuaded to go ahead and create a show around the character of Fletcher. Various titles such as Bird and Stir were banded about for the prison-based show before the writers settled on yet a third epithet used by criminals to mean incarceration: Porridge. The resulting show immediately became one of the all-time greats, with memorable, believable characters, richly comic dialogue and cunning plots.

Each episode began with the noise of prison doors slamming shut and the ringing tones of a judge (voiced by Barker) sentencing Fletcher to prison for five years. This set the tone: habitual criminal Fletcher is returning to jail for yet another stretch, although this time he is determined that it will be his last. Hoping his senior status will snag him a single cell, Fletcher is forced to share with a first-time offender, Lennie Godber, a naive, scared Birmingham lad. Unintentionally, Fletcher becomes a father-figure to the young man, steering him through the choppy waters of prison life. Although the pair aim for a quiet time, they invariably clash with authority in the shape of the kindly, well-meaning and easily swayed guard Mr Barrowclough, and the harsh and suspicious, everything-by-the-book Scots warden Mr MacKay. Sometimes it is Fletcher's sharp tongue that gets them into trouble, or his incorrigible criminal leanings, at other times it might be Godber's naivety - but, whatever the cause, more often than not it is fate and circumstance that lands them in trouble with the officious MacKay. But, by using all his guile and prison experience, Fletcher usually manages to extricate them, hoping - and usually succeeding - to score 'a little victory' along the way, something to cling to in the long, dark hours behind bars. In essence, Fletcher's advice to Godber, born of his long prison experience, is the two-fold 'bide your time' and 'don't let the bastards grind you down'.

Fletcher's common-sense and reluctant humanity mean that he is held in some regard by many of his fellow prisoners, but his guile cuts no ice with Harry Grout, the Mr Big among the convicts, who seems to have as much say in the running of Slade Prison as the governor and wardens. Some of the sharpest plots found Fletcher treading a tightrope between Grout and MacKay, having somehow to find a way to appease both parties. Other recurring characters in the show included the dithery Alzheimer-suffering old man 'Blanco' (brilliantly portrayed by the young David Jason); the thick-headed Yorkshireman Heslop; the gay 'Lukewarm'; the antagonistic black Scotsman McLaren; the guileless Warren; the disgraced dentist Harris; the weaselly and conniving Ives (who always began speaking with the words ''ere listen!'); and, of course, the Slade Prison governor, a somewhat over-gentle soul whom Fletcher had wrapped around his finger.