The term 'comedian's comedian' could have been coined to describe Sean Lock. Not only hugely popular with the viewing public, Lock was also highly regarded by fellow comics. In a moving tribute written for The Guardian, Harry Hill said of the last time he shared a bill with Lock, "I looked round and all the comics had come out to watch him. We don't do that for just anyone. If you tell jokes for a living it's hard to enjoy a comedian in the same way that a punter would, because you know all the tricks, you can see where a gag is going and often arrive at the punchline long before the comic telling it. Not so with Sean, that's why we comics loved him".

After performing his first gig in 1988, Lock built up a strong reputation on the comedy circuit. As well as his own stand-up, he also wrote material for Is It Bill Bailey? and formed an especially strong writing partnership with Mark Lamarr, with whom Lock worked to write material for Never Mind The Buzzcocks.

He also appeared alongside Lee Evans as an unnerving hitchhiker in The World Of Lee Evans and as various characters in Caroline Aherne and John Thomson's 1993 sketch show The Full Monty. Although Newman & Baddiel get the credit for being the first comedy act to play Wembley Arena, that honour technically belongs to Lock - he was their support act. He also had a long-standing association with filmmaker Andrew Kotting, co-writing and starring in his unsettling short film Smart Alek alongside Simon Munnery and long-time Comedy Store stage manager Stan Nelson, in 1993 and co-writing the screenplay to Kotting's 2001 drama This Filthy Earth.

15 Storeys High began life in 1998 as a BBC Radio 4 sitcom called 15 Minutes Of Misery. The show was scripted by Lock, who also starred. The conceit was that he lived in a high-rise tower block, his main source of entertainment being the lives of his neighbours, eavesdropping on their activities through the secretion of Bugger King listening devices in their flats. This allowed for a series of sketches to play out, from one-liner gags to longer jokes. Kevin Eldon and Hattie Hayridge played various characters, and the show was crammed with surreal visual ideas, for example: "I got pickpocketed this morning - by a bungee jumper."

A second iteration of the format, 15 Storeys High, expanded the show to half an hour per episode and saw Lock joined by Martin Trenaman to write the scripts. Dispensing with the eavesdropping conceit, voiceover was instead used to indicate the flat number, and Lock's character was now called Vince: a misanthropic, sardonic lifeguard. Errol was introduced as his flatmate, voiced by Peter Serafinowicz, while Jenny Éclair and Tracy-Ann Oberman joined the cast.

The BBC Three television adaptation, first aired in 2002, retained the basic setup of the radio show, with Vince working as a lifeguard at the local pool. It was once again written by Lock and Trenaman, with Lamarr - credited under his real name, Mark Jones - acting as script editor and credited as a writer on the second series.

The pilot episode had a laugh track, but this was dropped when the show went to series. Their scripts took the mundanity and minutiae of modern life and applied a surreal slant which was nevertheless always grounded in a cold, hard reality. A good example is the second episode, in which Vince teaches a Playboy model how to swim. Instead of being lecherous or lascivious, Vince is more interested in the model of the cupboard she poses in front of! In the same episode, her jealous boyfriend pays him a visit, but when faced with the alleged karate practitioner, Vince's reaction is one of resigned disdain and annoyance rather than fear.

One of the best jokes is Vince's habit of regurgitating other people's anecdotes or news stories as his own. This leads to one of the funniest and most unsettling sight gags in the show, in which he recounts a traumatic experience with The Wombles on the set of Jim'll Fix It. Other sitcoms may have played a scene like this as broad slapstick comedy, but the morose voiceover mixed with slow-motion camerawork means the scene plays out like a horror film, or a survivor recounting his experience of war.

It would be easy to describe Vince as a misanthrope but that would do a disservice to Lock's writing and acting, as he is far more nuanced than that. Vince is certainly not a happy character, but his twisted, insular worldview means that he gets joy out of things like hurling a pizza at a wall because it arrived with an olive on it, then writing a long-winded letter to the company. Or the time he goes to great lengths to track down out of date ham because a colleague is pinching his sandwiches and he wants to poison them. Another episode sees him write letters full of snide abuse to celebrities like Jimmy Somerville and Wayne Sleep. His frequent run-ins with neighbours and strangers alike also reveal an aversion to verbal abuse; not because he's offended by it, but he gets more irritated about badly thought-out insults than the insults themselves - an adage repeated more than once is "I don't mind abuse, as long as it's accurate".

Also carried over from the radio series is Vince's eternally optimistic flatmate Errol. Benedict Wong took over the role from Serafinowicz, who still appeared in the series as various other characters. Wong had previously appeared in an episode of Serafinowicz and Robert Popper's Look Around You, and explained in a Guardian interview that "basically [Peter] just did an impression of me, so when I turned up they sort of gifted me the part". He would go on to appear in sketch series The Peter Serafinowicz Show.

Vince And Errol's relationship is reminiscent of The Odd Couple, with Errol as the optimist and Vince the pessimist. Their comic chemistry is clear from their very first scene, in which Vince is immediately irritated that Errol has the audacity to want to share his sofa. Vince is irascible while Errol is innocent, coming across at times like a naïve child in an adult's body. Take the subplot in Episode 2, where Errol surreptitiously steals wallpaper from Vince's bathroom by stuffing it down his pants in order to decorate his own room. Wong is a superb comic actor, and a lot of the laughs come simply from watching his reaction to the weirdness around him. His naïvety also lands him in trouble: one episode has him eager to learn how to drive, but he is soon in a state of near-nervous breakdown while practising the emergency stop.

A selection of other oddballs populate Vince and Errol's tower block. In a move that is more readily associated with animated sitcoms like Family Guy, the camera frequently cuts abruptly to other flats, giving the writers complete freedom to take a gag in any direction, no matter how silly or surreal. Take the man who attempts to open a drawer, only to find there's a fish slice stuck in it, resulting in his increasingly exasperated and anguished cries of 'Oh Jesus Christ!" - this character was originally featured in sketch show Comedy Nation, in sketches written by Simon Godley and regular Paul Merton collaborator John Irwin. Or the man attempting to record a relaxation tape, only to be continually interrupted and subsequently exploding with anger. In this sense, 15 Storeys High is as much a sketch show as it is a sitcom.

Some of these sketches recur, while others are one off gags. Such a device allowed for surreal jokes to play out without disrupting the main narrative, like the old man in his vest and pants whose only scene is of him practising kung fu in front of a mirror. On an interview recorded for the DVD release, Lock explained of their ethos: "Nothing could happen in the flats that wasn't physically plausible, or socially plausible. You couldn't have someone living with a penguin." He was well aware of what the audience would accept and find credible, even within the context of a surreal scene.

However, for all its surrealist overtones, 15 Storeys High is crammed with outright jokes. Take the moment where Vince attempts to check in for a flight and gets angry after being is told it has been overbooked. "There's no need to swear," the attendant says. Vince replies: "There is a need to swear, oh very much so. It's situations like this that swearing was fucking invented for!"

Many of Lock's contemporaries on the comedy circuit appear throughout 15 Storeys High in guest roles. The late and much missed Felix Dexter plays a man who goes too far in his dedication to spreading the word of Jesus in Ice Queen. A cutaway in the same episode sees Paul Putner attempt to appease clean freak Toby Jones. Peter Serafinowicz, Kevin Eldon, Bill Bailey, Michael Smiley, Rob Rouse, Dave Cohen, as well as co-writers Trenaman and Lamarr, also feature in various episodes.

Credit must also go to director Mark Nunneley and production designer James Dillon, who made Vince's world as drab and dreary as a 1950s kitchen sink drama. Every directorial decision serves to emphasise the comic counterpoint between the setting and the surreal scenarios within. This was especially apparent during the cutaways to the neighbours, in which very often there would be no edits at all. Nunnelly would let the scene play out; as the situation escalates there is no escape, the camera turning the audience into voyeurs as we get a fleeting glimpse of fellow residents' lives. Nunnelly's work resulted in a nomination for Best New Director at the BAFTAs in 2003.

The enduring cult popularity of 15 Storeys High only goes to prove how hard Lock, Trenaman and Lamarr worked on the scripts. Lock was ruthless in the writing room and it paid off. Trenaman said in an interview that "if it wasn't right, it wasn't going out. That was the bottom line. I remember we'd work on something for five or six days, and I'd come in at 10 in the morning and Sean has deleted the lot. I'd say, 'Sean, there was some good stuff in it!' He'd say, 'No, it doesn't work.' We'd be right back to the beginning again".

Lock said in a 2008 interview with Den of Geek that he was disappointed with "the way it was tossed away by the BBC. I just thought you put in all that work and you're at the mercy and whim of someone who doesn't know what they're doing".

Although he never penned another sitcom, Lock did continue to write screenplays. In the same interview, he commented on a film script he was working on about the realities of being a stand-up comic; sadly it was never produced. Answering questions for this article, Trenaman also revealed that he and Lock were once commissioned to write a screenplay set in the world of darts.

Lock went on to achieve huge success on 8 Out Of 10 Cats and found an especially fruitful outlet for his style on the spin-off format mash-up 8 Out Of 10 Cats Does Countdown. The show generated many classic comedy moments, from Sean's stew - which led to an ill-advised whelk eating challenge - to his legendary prowess playing Carrot In A Box.

15 Storeys High, meanwhile, continues to be something of a cult curio beloved by those who know it. At the launch of Series 2, Armando Iannucci wrote of the show "15 Storeys High is difficult to describe, because it is unlike any other sitcom. The last comedy I can remember that arrived with such a perfect, idiosyncratic and fully formed comic world of its own was Father Ted. It's that good. I want you to watch it so much it hurts."

Perhaps more than any other sitcom since the turn of the century, 15 Storeys High deserves to be rediscovered and claim its place on the list of truly great comedies.