What have been the all-time game-changing TV comedies? I Love Lucy in the 1950s definitely; the social realism of Till Death Us Do Part in the 1960s perhaps; and then onwards through the decades by way of the absurdist humour of Monty Python and the long character story arcs of Cheers. And then on a Monday evening early in the new millennium – the 9 July 2001 to be precise – a sitcom by first-time writer-directors and set in the Slough offices of fictional paper merchants arrived completely unheralded on BBC Two. The Office would go on to change TV comedy for the next 20 years.

With no laughter track and borrowing the style of the then ubiquitous “docu-soap”, a genre kick-started by the 1997 fly-on-the-wall series Driving School and often coming with similar blandly descriptive titles like Airport and Vets in Practice, an urban myth has grown up that there were those who initially didn’t even recognise The Office as comedy.

Most of us certainly wouldn’t have recognised the cast – the now very well-known likes of Martin Freeman, Mackenzie Crook, Lucy Davies and of course Ricky Gervais – who wrote and directed The Office alongside Stephen Merchant. The title sequence featuring the drab, brutalist exteriors of Slough – the roundabout, bus station and office blocks – set to the wistful Mike D’Abo song “Handbags and Gladrags” (as sung by Scottish rocker Fin Muir) also didn’t offer many clues that a sitcom revolution was afoot.

The interior setting (actually an unused office at the BBC’s Teddington Studios) was instantly recognisable as somewhere we might all have worked at one time or another– a beige universe of trilling phones, paper being shuffled and (this being 2001) the occasional churning of a fax machine. Watching today, over a year into mass working-from-home, The Office might either induce wistful longing for a lost communal way of being or wonderment at how we ever spent our lives in such crummy environments.

The manager David Brent (Gervais) sees himself as an entertainer and all-round brilliant boss even when making grossly unsuitable remarks to receptionist Dawn (Davies); equally self-deceiving is bored sales-rep Tim (Freeman), who tells himself that this isn’t his destiny as he bickers over the stapler with desk-sharing creep Gareth (Crook).

“It captured that particularly modern form of the office – that late-capitalist, neo-liberal mixture of ennui and anxiety,” says Ben Walters, who wrote about the show in a book for the British Film Institute’s “TV Classics” series. “The double bind of being stuck in this god-awful situation that might be taken away from you at any time.”

The naturalistic depiction of mundane everyday life at Wernham Hogg was helped by the absence of a laughter track but was chiefly enhanced by the then-innovative “mockumentary” format, the characters acknowledging the cameras with a sly glance or (in Brent’s case) a full-on cheesy grin. Although the mockumentary form had been around for a while, most notably in the films of Christopher “This Is Spinal Tap” Guest – The Office was the first time many television viewers had experienced it.

“The characters’ acknowledgement of the camera really upped the cringe factor,” says Walters. “When you had them looking into the lens, looking right at you, that really pulls you into the situation in a really uncomfortable way.”

Indeed, along with Steve Coogan’s Alan Partridge and Garry Shandling’s Larry Sanders, The Office marked the genesis of a whole new genre that came to be known as “cringe comedy”, and nowhere was this more cringey of course than when Brent was tying himself into knots of political correctness when faced with non-white or disabled characters. “We thought it was interesting to write about the hypocrisy of people who think they’re politically correct, and the resultant awkwardness when they try too hard,” as Gervais put it at the time.

Brent may have been what Walters calls a “pathetic ogre” in the tradition of Captain Mainwaring and Basil Fawlty, but over the course of two series and a brace of Christmas specials, he went on a redemptive journey – the tragic clown getting a reprieve. Importantly, there was compassion here as well as cringe. But if you were looking for the real heart of The Office, it was to be found in the romance between Tim and Dawn.

“The traditional sitcom storytelling mode is circular,” says Walters. “By the end of the episode everyone is back where they started. But in terms of David Brent’s career and Tim and Dawn’s romance, it does develop.” Indeed, Richard Curtis, whose sitcoms include Blackadder and The Vicar of Dibley, has said of The Office: “It got better in ways I hadn’t expected… that it would have proper tragic and romantic dimensions was a shock.”

“We intended the show to have a happy ending, but we wanted it to be moving and uplifting without being mawkish,” Gervais has said, and Walters reckons the Tim-and-Dawn romance was innovative in British sitcoms. “There had been these big US sitcoms – Friends especially – where the romantic plotting had become as important as the comedy,” he says. “And having the presence of the cameras being acknowledged added another layer to the office flirtation, with cameras picking up every little glance and touch on the shoulder. It upped the ante and made it more suspenseful and affecting.”

With a total of just 14 episodes – two more than the similarly self-truncated Fawlty Towers – The Office has been far more influential than John Cleese’s comedy classic. This is partly down to the huge success of the American remake, which ran for nine seasons and made a star of Steve Carrell, while four failed attempts were made at transporting Fawlty Towers to an American setting.

Arguments have raged ever since about which of the two versions of The Office is the better, a pointless dispute that Gervais deflated in a recent podcast when asked about how he felt about claims that the US version were bigger and better. “F***ing rich,” he responded (Gervais and Merchant were executive producers of the American remake and therefore earned a considerable payday from it).

But it’s The Office’s mockumentary approach that has proved most influential – a style now so ubiquitous in both British (This Country, Pls Like, People Just Do Nothing, Twenty Twelve, Come Fly with Me and so on) and American sitcoms (Modern Family, What We Do in the Shadows, Arrested Development, Parks and Recreation, etc) that David Baddiel was once driven to complain about “this idiot idea that this is the only sort of sitcom we should have”.

But if the likes of Miranda and Mrs Brown’s Boys have since clawed back some of the demand for traditional studio-audience sitcoms, the mockumentary goes from strength to meta-strength – one episode of Disney+’s WandaVision even being a pastiche of Modern Family and The Office.

And all this has its roots in a goatee-bearded middle manager with a talent for self-deception. If there is another reason that The Office has stood the test of time, reckons Walters, it’s because its chief protagonist, with half an eye on the camera and in constant need of affirmation, anticipated social-media culture. “David Brent was very much an early adopter who took very seriously creating a narrative and self-image though being filmed,” he says.

“Here was this pathetic micro-celebrity but David Brent loved it and was all over it, and while he was not very good at it, actually that was the future and we all live in it now. To a greater or lesser degree, we all keep an eye open for where the camera is. Pathetic as he was, unfortunately these days most of us are David Brent.”