We all know the famous sketch. A suave, young John Cleese in a bowler hat looks down on Ronnie Barker, asserting 'I look down on him, because I am upper class.' Barker in turn looks to him: 'I look up to him, because he is upper class, but I look down on him' - he turns to look down at a young Ronnie Corbett - 'because he is lower class. I am middle class,' he announces as he looks directly to camera. Corbett, comically dressed as an urchin, does the same, as he declares 'I know my place.'

Most could identify this as the oft-repeated class sketch from The Frost Report. However, a simple question often lingers: what exactly was The Frost Report? For a series that played a pivotal role in creating legends and shaping the comedy landscape of the next few decades, very little outside of this iconic sketch has been in the public domain since its initial broadcast, which only enjoyed a relatively short run from 1966 - 67.

The title, The Frost Report, refers to David Frost: a journalist, writer, producer and comedian who became known the world over for his series of interviews with disgraced US President Richard Nixon in 1977, colloquially referred to as simply Frost/Nixon. These sensational interviews (which Frost funded himself, as American television networks were not interested in supporting them) delved into the Watergate Scandal, Nixon's personal life and the legality of his actions. Frost probed Nixon in a way no other journalist would have dared, with the resulting programmes attracting 45 million American viewers - still a world record for the most viewers of a political interview in history - and have been the subject of many plays and films since.

Michael Grade said of Frost, who died in 2013: "He was kind of a television renaissance man. He could put his hand to anything. He could turn over Richard Nixon, or he could win the comedy prize at the Montreux Golden Rose festival."

Now predominantly remembered as a legendary journalist rather than for his significant contributions to entertainment and comedy, television was, predictably, where Frost started out. After university he found work at Associated-Rediffusion (the ITV broadcaster of the day in London), and was chosen to host a brand new satirical comedy. The year was 1962, and the BBC had just commissioned a pilot inspired by the sketches that were being performed at Peter Cook's The Establishment - a club based in Soho where satire was the order of the day and stars such as Eleanor Bron, John Bird, and John Fortune regularly performed.

The fact that this idea was reworked into a vehicle for David Frost was something that Cook reportedly resented, thus beginning a rivalry between the pair: at one time Cook dubbed Frost 'the bubonic plagiarist', so jealous was he of the success of the resulting show, That Was The Week That Was (regularly shortened to TW3) - a series that would change the television landscape forever, bringing satire to mainstream audiences.

Frost's involvement came about thanks to John Bird (Frost's flatmate and Cambridge University alumnus, who would later find the height of his own fame in satirical sketch show Bremner, Bird And Fortune). He had persuaded the show's creator, writer and producer Ned Sherrin, to see David Frost performing live, after which he was duly signed up.

That Was The Week That Was broke new ground and is still the blueprint for almost every satirical variety series. It was dry and intelligent, making no attempt to pander to its audience. It took breaks for debates, while surrounding serious moments with sketches and songs - It was not afraid to be silly, it was not afraid to be serious. Sometimes the audience seemed genuinely unsure of how to react, the humour was so understated.

One sketch in the first episode sees Frost interview a supposed cartoonist about his life:

'You have an amusing time, but not much time for leisure?' Frost asks earnestly.
'Well, what leisure time I do get I spend dreaming about living on a very small desert island with only one palm tree,' he tells Frost seriously, while he draws this for us and nods.

The audience are simply unsure what to think or how to respond. It feels like the origins of the bizarre, irreverent satire of Chris Morris's The Day Today (1994).

The writing and performing talent were of the highest calibre. Over the course of its two series, sketches were penned by Graham Chapman, John Cleese, Peter Cook, Roald Dahl and Eric Sykes amongst many others. And it was this eclectic mix that brought in humour from across the spectrum of comedy, politics and society. The show was a hit, featuring beloved performers of the day, such as Hattie Jacques and Roy Kinnear, in sketches that underpinned each episode.

Even Peter Cook (who later started writing for the series) put aside his feud with Frost, after a dramatic turn of events saw him step in to save David Frost from drowning in a swimming pool. Alan Bennett joked at the 1995 memorial service for Cook that rescuing Frost was the one regret he frequently expressed.

Despite overwhelming positivity in its reception amongst both audiences and critics, the BBC did receive complaints about TW3. Prime Minister Harold Macmillan had initially been supportive of the show, but it soon became a bone of contention amongst MPs; but after American President John F. Kennedy was assassinated, the episode being recorded and broadcast the very next day changed its tone entirely and became a tribute, exhibiting the programme's power and ingenuity.

The show was effectively axed in 1964, with the BBC offering the simple explanation that it was a General Election year. No more was said about the series returning. Frost took the format to America, where TW3 ran for one series and a special, That Was The Year That Was, a comedic recap of the last twelve months.

Frost's next project was another series produced by Ned Sherrin, Not So Much A Programme More A Way Of Life - one of the longest programme titles in television, it was at least shortened to the much more catchy NSMAPMAWOL (pronounced Ens-map-may-wall).

Ens-map-may-wall saw Frost and Sherrin attempt to build on the success of TW3. Frost co-presented the show with Willie Rushton and the poet P. J. Kavanagh. It was also notable for some of the first major television appearances of John Bird, Eleanor Bron, Roy Hudd, and John Fortune, and featured Michael Crawford in a regular spot as 'Byron'. It was popular and ran for a stonking 62 episodes in 1964 and 65, but once again proved too much of a hot potato for the BBC - one sketch provoking particular ire for being disrespectful to the Royal Family - and did not return after that (admittedly very lengthy) single series. However, Frost was undeterred and he returned just a year later with another format: The Frost Report.

The Frost Report took an approach to satire that was far less directly political - an ingenious way to swerve controversy. Frost did not focus on Parliamentary matters or ministers: this wasn't about simply giving the government of the day, or indeed the opposition, a good kicking. This was Frost taking a more abstract and timeless approach to satire, with each episode focused on and themed around a specific topic. As such, the series took a sideways look at concepts that are the fundamental building blocks of society - such as law, money, love, education and sin - and analysed them in a non-partisan way.

In the pilot, he and his team explored authority: 'Authority tries to protect its position by the language it uses,' Frost tells us in a piece to camera. 'It never means what it says: "the matter is under consideration" means "we have lost the file"; "the matter is under active consideration" means "we are trying to find the file". It's the same with all other statements.'

We then see observe a series of cutaways between the Two Ronnies and John Cleese delivering statements, and back to Frost who tells us what they really mean:

Barker: It is not in the public interest to do this.
Frost: Means, it is in the public interest to do this, but not in ours.
Corbett: Public feeling is not yet ready for such a step.
Frost: Means, public feeling is ready for such a step, but we're frightened of The Daily Express.
Barker: This is an urgent problem, and we are therefore setting up a Royal Commission.
Frost: Means, that we hope in three years time, everyone will have forgotten about it.
Cleese: In the fullness of time ...
Frost: Means, never.
Cleese: In the not-too-distant future.
Frost: Never.
Cleese: Never.
Frost: As soon as we dare.

By any decade's standards it was a fantastic start. Frost's monologues were honest and straightforward: they certainly seemed to be his genuine musings on the subject at hand. He and the writers, headed by Antony Jay (future co-creator Yes Minister) clearly felt no need to moderate the show's satirical points for the BBC now that it steered clear of the directly political. The sketches, which were often no more than a few seconds long, benefited hugely from the talents of Ronnie Barker, Ronnie Corbett and John Cleese, three people who would become legends of the sketch genre in the years that followed, and with hindsight it's clear that some sketches stray directly into the territory of Python or The Two Ronnies. One sketch sees Corbett and Barker as policemen:

'Good morning, Super!' Barker says as he ambles up to Corbett. 'Good morning, wonderful,' he replies.

A quick cut back to Frost catches him laughing at this, 'They won't tell me what that means,' he laughs, perhaps sensing the start of something between the pair. This, right here, was the origin of their double act.

The famous class sketch appeared in the fifth episode of the series, which was, somewhat unsurprisingly, titled The Frost Report On Class.

'What is class?' Frost asks us. 'Class is the ladder in the social stocking,' he says. 'It's having grapes on the sideboard, even though there's nobody ill,' he muses; and throughout the episode, Frost makes the point that the class system always seems to be with us, whether we like it or not.

But the question remains, why is the class sketch the sketch we always see? What made it so important? Oddly, there's nothing in particular that causes it to leap out at you in the context of the episode. Frost introduces it quite simply, segueing from another point he says, 'But how do the classes see each other?'

And the sketch itself does not stand out more broadly, as it is indicative of The Frost Report's style. All the sketches of the series were direct, to the point, and, if we're honest, accurate in their speedy analysis of society - not just then, but interestingly, now. They are as incisive and precise as a surgeon's scalpel. Never the less, somehow this one has proven emblematic. Written by Marty Feldman and John Law, the sketch was cited by The British Film Institute as being of cultural importance. They commented:

'Its twinning of height and social position, combined with a minimal script, created a classic TV moment. The sketch's influence has persisted to the present day, having been referred to in 21st-century discussions of politics, sociology, and even football.'

Now often cut short, the full sketch ends with Ronnie Barker declaring:

'We all know our place, but what do we get out of it?'
'I get a feeling of superiority over them,' Cleese explains, looking down over the two Ronnies.
'I get a feeling of inferiority from him,' says Barker, as he looks up to Cleese, 'But a feeling of superiority over him,' he gestures down to Corbett.
Ronnie C then delivers the punchline: 'I get a pain in the back of my neck.'

Ronnie Barker was such a fan of the sketch that he wrote three follow-ups in the same style for later Frost Report episodes. He and Corbett would perform it again in 2000, this time with Stephen Fry in place of Cleese, as they satirised three periods in history (present day, the Renaissance and the Middle Ages). John Cleese also paid homage in 2017, this time Americanising the subject.

And that is the enduring legacy of the sketch, putting the class system in such bold terms highlighted both the ridiculousness and the ultimate inevitability of it, whatever the decade, be it the sixties, the dawn of the new millennium or even now.

It seems every comedian, sketch show or sitcom needs its defining 'moment'. Python had the dead parrot sketch, The Two Ronnies had their four candles, Mitchell & Webb wondered if the Nazis ever asked 'Are we the baddies?', Father Ted gave us a lecture on cows we will never forget, Pike's name went on the list, Del Boy fell through the bar, David Brent performed a little dance, Eric Morecambe played all the right notes, but not necessarily in the right order, the cast of Goodness Gracious Me went out for an 'English' and Hancock gave blood.

Frost, himself, had little to do with the class sketch, yet he hardly seemed to mind. His illustrious career continued apace and he consolidated his role as an interviewer shortly after The Frost Report's end. This heralded his drift away from the comedy world, as he became more and more successful as a serious journalist.

In his lifetime, David Frost would interview eight British Prime Ministers (Harold Wilson, Edward Heath, James Callaghan, Margaret Thatcher, John Major, Tony Blair, Gordon Brown, and David Cameron) and seven US Presidents (Richard Nixon, Gerald Ford, Jimmy Carter, Ronald Reagan, George H. W. Bush, Bill Clinton, and George W. Bush). In between all this, he found time to present Through The Keyhole, which ran on various channels between 1987 and 2008. The series was revived in 2013, where Frost was replaced as host, perhaps somewhat oddly, by Keith Lemon.

It's clear to see what an enormous affect The Frost Report had on modern satirical comedy shows. From Brass Eye to Newswipe With Charlie Brooker, from 10 O'Clock Live to The Mash Report, from Spitting Image to Dead Ringers, all have taken their cue, to a greater or lesser extent, from Frost. He had shown, with great skill, how to tackle tricky topics and find the humour in them. Taking a tricky subject and robbing it of its sting with daftness - that, in essence, was the enduring power of the iconic class sketch, and of The Frost Report.