If pressed, when asked which class we are in, most of us would reach for a placing that fitted on one rung or the other of the old hierarchy in this country. We would be more comfortable talking about the class of our parents and even more confident cataloguing our grandparents. Yet while class has been a most useful social marker in these islands for centuries, it is now, I suspect, well on the way to losing its authority to culture.

People today are more comfortable identifying themselves by their cultural choices than by their class. They are likely to say "I'm a Radio 4 person" or that they like grime, or jazz, or film, or opera. The class barricades have been stormed by the forces of a broad culture, which is made up of clusters of individuals who have decided for themselves what they will be in society. They can't be bothered with the labels and designations of the ancien régime.

As the 20th century unspooled, a cultural warming melted down many frozen class characteristics. A hundred years ago, the upper classes literally owned much of what was understood as culture – architectural masterpieces, great paintings, a superior style, the opera, the ballet. Today, even though some of that remains, most of it has slipped out of the hands of the aristocracy.

In 1911, it could seem that the three established classes were at their most triumphant. The ruling classes were clad in splendour, in charge of big red chunks of the map, developing the arts of leisure and still cultivating high magnificence in architecture, the amassing of art and their gardens. The infusion of new money to replenish the bloodlines and the coffers stopped the arteries furring up. The upper classes made very little art, although they could effect change: it was an aristocrat, Lady de Grey, who brought over the Ballets Russes that year. Curating was the thing and it was pursued with energy and often with fine taste. There were more than one and a quarter million domestic servants to see that the elite were released into the leisure that this demanded.

The middle classes took their fair share of the servants and aped the aristocracy in dress, manners, accent if they could, and many of the leisure furnishings of life. The seaside became their domain. (It would only later be passed on to the working classes.) The gentleman was at large. Being a gentleman, as the aspiring protagonist discovers in H G Wells's novel Kipps: the Story of a Simple Soul, is a full-time occupation.

Where the middle classes differed from the aristocracy was that they made things or supervised the making of things. In much of culture, they were the doers, the drivers. They made the conquering novel their own and until fairly recently it remained that way. Although working-class exceptions such as D H Lawrence tested the rule, the middle class provided most of the painters, the poets, the composers, the movements, the -isms. It became an ever-broader and confident caste, though furrowed by minor but deadly distinctions.

Cockles and muscles

One thing that united the middle class, broadly speaking, was its fear and loathing of the working class. Those who had risen from it were fearful they might fall back through the cracks. Those who thought they were above it could be vicious. You see it most plainly, as often happens, in converts such as Wells, whose Morlocks in The Time Machine portrayed a future class of workers who were violent, without morality and vicious – a strain of spite that persists today. John Carey develops this authoritatively in his book The Intellectuals and the Masses. The working classes were characterised as feral, dirty, uncouth and ill-spoken, with no culture worth the word.

As a view from above, it was a comfort to the established. Yet it was ignorant, perhaps wilfully so, and wrong. At that time, still about 1911, the stronger part of the working class had forced its way into an impressive garrison culture. There was fine music, with choirs singing works from the masters of choral music, and brass bands, the orchestras of the working class, were commissioning Elgar, Holst, Vaughan Williams and others. There was the spunk and comedy and creative vitality of the music hall, which would wind through to the full, commanding force of popular culture half a century later. There were chapels with a hard-headed, Nonconformist culture in language, religion and education, with Sunday schools and reading classes. Reading rooms were common, as were mechanics' institutes, and the libraries became the universities of the poor. Their trades unions, like their sports, football and cricket, were well organised; their ambitions were high.

But this was not the whole story. There were many of the poor just too poor to have the energy or the means to participate in most of this. And the unions were making their muscle count in strikes and threats that troubled, as they were meant to, the status quo.

It is often argued that the Great War was the first and biggest detonator of the old class system and by association of the culture, but I am not so sure. Middle-class painters depicted most vividly the courage of the lower ranks. Middle-class poets turned on the ruling class and their middle-class peers. Among them, too, were men of classless heroism and Rudyard Kipling's vision of one sceptred nation united in a noble cause and embracing a common death was, for some, a bringer of equality. But after the war, it soon subsided. All the classes had been depleted but they remained intact. The worlds of P G Wodehouse and Evelyn Waugh were unchallenged in their celebration and loving satire of the upper classes. There was nothing approaching a revolution from the lower depths. The middle class held on and ground on. The air did not yet go out of the balloon, even though the grand imperial flight of Britain was beginning its plunge to earth.

Two innovations would begin a papering-over of the class gaps; developments that would, in their wider effect on the culture, go a long way to sidelining the old distinctions. One was public dancing, which may well have kicked off when ragtime came from the United States to the Savoy in the 1920s. This spread with epidemic intensity across the country and soon hundreds of thousands of people were ballroom dancing. The upper classes were mad for it. The middle classes built suburbs of culture around it. The working classes were swallowed up in it. And they all danced to the same tunes, in the same ways, with the same regimen of decorum and politeness and transparent though restrained public sexuality. Pleasure was a unifier.

When "The Lambeth Walk" turned up in the 1930s, it became an alternative national anthem. Even the king and queen did it. You could say the lower orders had taken the dancing gift of the uppers, claimed it and given it back with a satirical "Hoy!".

There was the ever-accelerating interest in the cinema, too. Here, again, all the classes enjoyed a rough equality. Seat-price differences were of negligible importance compared to the equal experience in the vast, dark room, watching the same images. American films appealed most, I think, because of their instinctive democracy. Like the dance halls, the big cinemas were built like palaces. We could all be posh now, if only for an evening. For ordinary people – not just the working class – to go from a slum or a modest little house to one of these immense, Viennese-imitation ballrooms or operatically decorated cinemas was to enter into a brave new world open to all.

The BBC was the odd one out. It ought to have been like dancing and the pictures, a potential unifier and a radical current in the rise of mass culture. But it adopted the three-tier system. Provincial accents were relegated to comedy, the rude mechanicals were not to be allowed at the top microphone and, wonderfully, the Light Programme, the Home Service and the Third Programme became the very replica of lower, middle and upper.

For the BBC, it seemed that the three tiers of class were in the genes – which is also how Lord (Jeremy) Hutchinson, QC described the retention of the public schools by the Attlee government in the 1940s. Many thought that their abolition was assured under the Labour prime minister Clement Attlee and his colleagues in their great, postwar reconstruction. This educational apartheid (Hutchinson's word) was expected to end. But Attlee was a loyal public-school man and he let the opportunity pass by. A chance to give his country an educational equality that could have changed it for ever was not taken.

It was a Tory politician, Rab Butler, who pushed through an act that opened up the grammar schools to thousands of children such as myself, who would otherwise have missed their often elitist but effective intellectual education. Grammar-school products began to shape a different Britain, as did those who later came from comprehensive schools. Look Back in Anger by John Osborne at the Royal Court Theatre in 1956 was a cultural shock. In what it was, what it represented and what it seemed to license, it has every claim to the useful cliché "watershed". It was a new voice on the London stage but it also represented a new tranche of art-makers: Kingsley Amis, Philip Larkin, Ted Hughes, Alan Sillitoe, Karel Reisz, Lindsay Anderson, David Bailey, David Puttnam and his gang, David Hockney and so on, into The Wednesday Play and the rise of television drama and comedy that would hold its own with anything in the West End.

The cultural axis in this country had shifted. Ken Loach's Cathy Come Home (1966) was an important example. What was happening in society, still class-ridden, was immediately taken into the culture – via television – which then influenced the society. In different ways, That Was the Week That Was and Private Eye began to pull down the old pinnacles. And then came the music, the class leveller: the Who, with Pete Townshend aware of the effect of the havoc he caused and the importance to the new generation of the lyrics with which he egged them on, and the Stones, who promised promiscuity for all.

From the ruins

It was the Beatles who nailed it. No longer could anyone condescend to working-class culture; no longer could anyone dispute its potential. Quality was staring us in the ears and class had to take a step back. It would not be a simple victory. The middle classes had their own Beatlemania in Covent Garden with Rudolf Nureyev and Margot Fonteyn and later in the West End there was the global takeover of musical theatre by Andrew Lloyd Webber and Cameron Mackintosh that drew on cultures both old and new.

The novel, long declared dead, would rise again. But the grit was still in the gingerbread. Tony Harrison's poem "Them and [uz]" and the other northern intransigent Viz marked both a resistance and a seed for progress inside the old working class. The 1970s ended with our dearest indicators of class – accents. There was the fake, raucous sound of the Sex Pistols and the faux posh of Margaret Thatcher. It was as if we were mimicking and were not quite sure where to go.

In the 1980s, the miners' strike and the Conservatives' response gutted the heavy industries of what had recently been the greatest industrialised nation in the world. They were laid waste – as the north so often had been – and with them went an immense culture of highly skilled craftsmen and unskilled workers who valued their place in a community of industry.

Out of the ruins was to come the partly engineered collapse of a working-class culture, its strongholds and structures undermined. At the time, it was a working class that had just settled into a revival with the Liverpool-led renaissance in music, drama, comedy, poetry and performance. Yet now it was lampooned, caricatured to the point of vilification, despised, a source of easy, nasty mockery, often by the young, liberal middle classes.

But all was not lost. Culture carried on defying class strictures to define the zeitgeist. In music, the Specials brought a city, Coventry, bombed out for a second time and riven with racism, to a celebration between black and white musicians and their music. The cultural rise of the lower classes would not be stopped despite the assaults on their position.

In the 1990s, from the estates of Scotland came the phenomenon of Irvine Welsh. Trainspotting demanded its place not only in the high ranks of contemporary fiction but as a describer of a Britain that literally and metaphorically was in a deep mess. Welsh told me he was "upper class. I'm an idle, rich person." Hockney (Bradford Grammar School) said of himself and his family: "We always thought we were first class." The ambition of the lead character in Billy Elliot typified the growing determination of those who had been outsiders to seize any opportunity and get on the cultural map. It also indicated the growing dedication of theatre, ballet, opera companies and museums to providing the opportunities.

In the past decade, Dizzee Rascal, Wiley and Tinchy Stryder showed how young, black artists, from the most neglected housing estates in London, could find a way through the culture to change it. They gave significance to people whose lives were thought to have none, people who were regarded as an underclass. Culture was doing what class never did – healing wounds.

What has happened with especial force over the past 50 years is that culture, especially popular culture, has forced itself on to the centre stage of the arts. The middle classes rise and rise. They draw in recruits from the old working class, the lower middle class and even the upper class who have had to downsize a bit. They exercise a central influence. It is often their gate money and donations that underpin the amazing bouquet of festivals throughout the land. They support what they see as the best in radio and television, newspapers and magazines.

So are we all middle class, or aspiring to be, now? A nation of culture seekers and keepers? More than ever before, I think, but that is not the nub of it. We want to design our place in society for ourselves. We are bored and fed up with the old props of class and prefer to take culture as our guide. Class will never go away but as more people find satisfaction in the increasing variety of culture, the less importance it has. It has been, over the century, a quiet but decisive revolution.

The three-part series "Melvyn Bragg on Class and Culture" begins on 24 February at 9pm on BBC