Writers Dick Clement and Ian La Frenais will forever be indelibly intertwined with Porridge, a series consistently voted among the greatest sitcoms ever made. Originating as one of the comedies made for the Ronnie Barker anthology Seven Of One (1973), the character of Norman Stanley Fletcher was created for him.

Comprised of seven individual, one-off comedy plays, the run was primarily intended as a showcase for the star's comic acting talents, but offered the secondary potential of acting as a pilot run: if any of the concepts proved successful enough on screen and popular enough with viewers, it would be considered for commissioning to series. And so both Open All Hours and Porridge came to fruition.

However, in an interview conducted with this website to mark Porridge's 40th anniversary celebrations in 2014, Clement and Le Frenais revealed that the history of British sitcom could have turned out very differently. Thick As Thieves (1974) was actually conceived and written before Porridge, as they developed ideas for Seven Of One, based around Barker's interest in telling the story of somebody coming out of prison.

They explained that "we started to write Thick As Thieves thinking it might be something for Ronnie. And then we couldn't stop writing! We had such fun with it. We were saying 'Is it a movie? Is it a play? Is it a television series?' We didn't know. All we knew was we were having a lot of fun writing it. Eventually it became a series, which was of course not fulfilling the commitment [to write a single episode]... So then we had to go to Ronnie and say 'You know that idea about a guy coming out of prison? We think it'd be better if it's about a guy going into prison'. And we really were caught in this dilemma - and then ended up selling Thick As Thieves to London Weekend Television".

The central premise of Thick As Thieves is a classic sitcom setup. Bob Hoskins plays George, who emerges from prison having served three years for burglary only to find that in the interim his wife Annie, played by Pat Ashton, has begun a relationship with his best friend Stan (John Thaw). When the latter is injured and cannot leave the house an uneasy truce begins, Annie finding herself unable to choose between the two men. It has to be said that the role of Annie is a pretty thankless one: not because she isn't given good dialogue, but the character is difficult to get a handle on and her attitude to both men grates as the series goes on.

It was the first sitcom for both Thaw and Hoskins, but being filmed in front of a studio audience was not dissimilar to the plethora of plays they had been in previously. As Clement and La Frenais note during the aforementioned interview, audience sitcom is a delicate art and it can really throw actors who hadn't done it before. Of Anne Bancroft in their later series Freddie And Max, they said that "she was really thrown - she didn't realise she was going to have to do it in front of an audience. So there she was, this fantastic legend, and suddenly the live audience really threw her. She was nervous".

George and Stan are classic Clement and La Frenais characters: the gruff, working class world-view mixed with the eloquence and loquaciousness of their speech, like when George complains "'Alf the Fulham filth are au fait with our affairs". Much of the opening episode is given over to an argument between George and Annie, and while it might come across as more Pinter than primetime sitcom, Clement and La Frenais are of course masters of their craft and intertwine character and comedy perfectly. Take this exchange between Annie and George:

Annie: George, you've been cut off from society for three years. From the social transformation which has caused a structural upheaval to the code of moral values which you once held so dear.

George: You never got that off Stan.

Annie: No, I got it from the New Statesman what I read in the dentists Tuesday. But it's true nonetheless.

Hoskins especially is electric on screen, exhibiting wonderful comic timing - something he took to his film work in the likes of Who Framed Roger Rabbit and Hook.

Thaw made Thick As Thieves just one year prior to becoming a household name in The Sweeney. In fact, the pilot for the legendary police drama actually aired in the same week Thick As Thieves made its debut - but the characters couldn't be more different. While D.I. Jack Regan was tough and uncompromising, Stan is sweet-natured, softly spoken and a bit of a pushover: it's easy to see shared DNA between Stan and Terry Collier from Clement and La Frenais's first sitcom, The Likely Lads. The fact that Stan and George were best friends adds an extra frisson to the characters' predicament, because although George is understandably angry, he cannot bring himself to truly cast Stan out of his life.

While the show is primarily a three hander, other characters recur throughout, most notably Johnny Briggs as mutual friend Spiggy. Briggs made his television debut alongside Thaw in 1956 drama series The Younger Generation, and later became a household name playing Mike Baldwin in Coronation Street.

Other familiar faces that pop up throughout the series include On The Buses star Michael Robbins as Sergeant Black, the local bobby who keeps his eye on the newly released Dobbs, and The Vicar Of Dibley's Trevor Peacock as an escaped convict.

Once the central conflict is established across the first couple of episodes, it begins to become clear why Thick As Thieves lasted for only a single series: although the quality was high, it is difficult to see how Clement and La Frenais could have wrung many further episodes' worth of plot out of the concept. Stan and George form a kind of Odd Couple dynamic as various plots see them try to do housework, as well as depicting George's run-ins with the police. And, relatively unusually for a sitcom of the time, Clement and La Frenais serialised the show, with continuous story arcs and plot strands, such as Annie planning a foreign holiday with Stan, running across multiple episodes rather than each existing in isolation.

Clement and La Frenais would revisit the same basic premise in Porridge sequel Going Straight, which saw Fletcher finally released from prison only to find former cellmate Godber dating his daughter, Ingrid. They would also explore the world of criminality again in various feature film screenplays, notably the 2008 heist film The Bank Job.

Despite showing a real flair for comedy, Hoskins played the lead in only one other comedy, a long-forgotten curio called Flickers, written by Roy Clarke and aired in 1980. Thaw, on the other hand, quickly found huge success on the other side of the thin blue line, as detectives in both The Sweeney and Inspector Morse, and became a sitcom favourite from 1986 to 1990 in Eric Chappell's Home To Roost.

Pat Ashton, meanwhile, was already a familiar sitcom face, albeit usually in far lesser, supporting roles, with a plethora of credits including On The Buses, Tripper's Day, Only When I Laugh and The Gaffer.

Thick As Thieves was eventually released on DVD by Network in 2009, and it is a curio that deserves reappraisal not just in light of its nearly-ran connection to the iconic and rightly celebrated Porridge, but for the scripts from two writers at the height of their powers, and comic roles for two titans of dramatic acting.

Although Porridge is likely to go down in history as Clement and La Frenais's career-defining masterpiece, Thick As Thieves is a worthy companion piece, and while there are many comparisons, it more than stands on its own as a fine example of tight comedy writing.