You visited some of Britain?s toughest jails to research the show. What was that like?

La Frenais: We visited Brixton Prison and met the governor, but after being shown around we felt really deflated, thinking we?d never find enough material to write an entire series. Clement: We also visited Wormwood Scrubs and Wandsworth Prison. We came out of the prisons and said to each other: "How the hell do we make a whole series based in prison funny?" At the end of the day, prisons are grim and we knew our show had to reflect that; it would have been dishonest and cheap to trivialise it.

So how did you approach the issue of bringing humour to such a bleak setting?

La Frenais: The one thing you could do on TV, probably better than any other medium, was to have an entire episode set inside a cell. Prison is about being locked up, so we decided to do this episode early on as a way of facing the fact that prison isn?t funny: Lennie being scared and depressed reflected the harshness of the situation.

The executive producer, Jimmy Gilbert, also introduced to you ex-con Jonathan Marshall. Was that helpful?

Clement: Just talking about the routine of prison life was valuable. Jonathan taught us a lot about the slang used in prison. La Frenais: Jonathan started telling us stories about being inside and kept using the phrase, "little victories", which struck a chord. Dick and I thought that maybe this was the key: we could make the show about a man with a fondness for earning "little victories" ? beating the system on a daily basis, even in the most trivial ways.

How did you come up with the title of the show?

Clement: We were in the editing room before we?d chosen a title for the series. Titles can be tricky, they either come to you or they don't. Ronnie came in and announced that he'd got the perfect one. "So have we!" we countered. A heated argument ensued for about ten seconds until we settled who was to go first. Ronnie won the coin toss. "Porridge!" he announced triumphantly. "That's our title!" we said. "Swear to God!" End of debate, dispute over, off to the bar!

What was it like working with Ronnie?

Clement: I wish we'd seen Ronnie extend himself more as an actor because I never saw limits to his talent. He brought with him a rare intelligence. First to the script, where his quick mind offered up new or improved jokes, always with great respect. "Is that all right?" he'd ask and as a rule, once we'd stopped laughing, we'd nod okay.

Is it true that Richard Beckinsale found the initial script readings difficult?

La Frenais: Richard didn?t seem like any actor I?d ever met, and whatever drove him didn?t appear to be fuelled by ambition and ego. The term "laid back" didn?t exist in the mid-seventies, but if it had there would have been a picture of Richard next to the dictionary definition.

He was a terrible reader, which is the first part of an actor?s investiture in a new role: the moment when he has nothing but a notion of the character and the unread, "cold" script. Richard was hopeless, it?s a wonder that he progressed from his earliest auditions!

He was even bad after he?d had the script for a few days and we all assembled for the cast read-through. Then something amazing happened, as it did every week when Richard?s performances went from hesitancy and incoherence to the truth and brilliance with which he invested all his work.

Fulton MacKay was another coup for the show...

Clement: He was a lovely man, brim full of life, love and enthusiasm. Syd Lotterby (the series producer) told me that Fulton would rehearse forever if you let him. It was true, but it came from a deep desire for perfection. I think it took us a few shows before we realised what a priceless asset he was, and what a brilliant adversary for Fletcher.

With so many comedy geniuses in the cast, it's quite east to overlook Brian Wilde (Mr Barrowclough)... La Frenais: Brian belonged to that stock of character actors whose work, understated and subtle, is consistently excellent and consistently unheralded. I think of Brian as the civil servant overlooked for his expected promotion; the man in the raincoat at the bus stop who?s jostled aside and left standing in the rain.

Brian?s characters don?t stand out in the crowd. They blend in with the background, camouflaged against the spotlight. A little like the man himself whom we never got to know really well but grew to respect with growing affection for his dry humour and superb acting instincts.

How did you feel about Ronnie?s decision to quit the show?

La Frenais: We ended with a kind of compromise by doing Going Straight. We just felt we couldn?t abandon the character ? people still wanted to see him. I think Porridge would have taken another series. Clement: I wasn't particularly disappointed. It was time to move on and I thought of the series with nothing but pleasure, because it really was totally painless.