Over a few months in 1968 Rebecca West, Stephen Spender, Frank Kermode, David Farrer and W. L. Webb gathered to discuss around sixty books. Sometimes they met at Bertorelli’s restaurant in London. Once they spent a weekend together at Michael Astor’s house in the Cotswolds. In West’s typewritten notes from that inaugural year of the Booker Prize, Michael Frayn was deemed “curiously dull”, Melvyn Bragg “grossly over-written” and Anthony Powell “not earth-shaking, I feel, because there is such a high percentage of twaddling on”. (The assessment of Powell, by the way, was as close as she got to a compliment.)

“Getting through the sixty was made easier by our not daring to take on Dame Rebecca”, Frank Kermode later remembered. The Booker archive at Oxford Brookes University holds many small white postcards from West, full of imperious putdowns in handwriting as tiny as her pronouncements are sweeping. “It is to be noted”, she scrawled, “that all the novels about Ireland yet submitted cause a feeling of regret that people are not killing themselves all over Ireland and not just in Ulster.” And so on.

The prize had been established some months earlier by the publishers Tom Maschler and Graham C. Greene, with the aim of emulating the Prix Goncourt, which unfailingly stimulated the reading of – and conversation about – new fiction. They found an eminently willing sponsor in Booker Brothers, once a Guyana-based colonial enterprise, then an enlightened business run by Jock Campbell, a socialist peer with a strong desire to compensate for the history with which his sugar-trading ancestors had been associated. Thanks to Campbell, and his golfing friendship with Ian Fleming, the Booker’s “Authors’ Division” held the copyright to the James Bond books, as well as to the works of Agatha Christie, Georgette Heyer and Harold Pinter. (The original impulse for these acquisitions was an admiring sort of bailout – not unlike, say, the Harry Ransom Center at the University of Texas buying up an author’s archive in his or her lifetime, with a strong injection of cash.)

Once the prize was established, the sponsors were routinely referred to in correspondence as “the sugar daddies”. One of the most infamous stories about the early history of the prize is John Berger’s donation, in 1972, of half of his £5,000 winnings to the British Black Panthers, as if in restitution for the origins of the money. His speech – flamboyant, and somewhat comical in its merely partial gift – was not as antagonistic as its disparaging reception suggested; a nuanced view might see that impulse as already baked into the purpose of the prize itself. Indeed, a sift through the archive reveals Berger’s apparently oppositional gesture to be part of its DNA.

Prizes can be a useful platform for protest: Jean-Paul Sartre declined the Nobel in 1964, setting in motion a tradition so strong that – as J. C. suggested in the pages of the TLS – there might be a Sartre Prize for the refusal of prizes. (“So great is the status of the Jean-Paul Sartre Prize for Prize Refusal that writers all over Europe and America are turning down awards in the hope of being nominated for a Sartre”, wrote J. C. in 2012.) An alternative to declining a prize was to use it to draw attention to something else. In 1973, the year after Berger won the Booker, Marlon Brando boycotted the Academy Awards and sent a Native American woman to turn down his Oscar for Best Actor. In 1968, the year the Booker was built, the American poet Robert Bly gave his National Book Award to the anti-Vietnam effort.

The founders of the Booker Prize knew this sort of gesture could confer distinction – as well as publicity. If you look at the correspondence about its inception, one of the most striking aspects is the Booker Prize’s association with revolution from the start. Jill Mortimer, who was working for the Publishers Association and conducting research in order to set up the prize, remarked that it had been difficult to get much information about the Goncourt prize because, in May 1968, the post from Paris was rather slow. W. L. Webb, Literary Editor of the Guardian and the Booker’s first chair of the judges, wrote to Mortimer from the road, going back and forth between London and Prague, where he was working with Václav Havel, then a dissident playwright, later the President of Czechoslovakia (and then the Czech Republic).

When Berger gave part of his money to the Black Panthers, a rumour circulated that the movement had already petered out. That wasn’t true; they hadn’t disbanded, they were just disorganized. The British Black Panthers were not – and never had been – a political party like the Black Panthers in the United States. They also had quite different goals. These were not African Americans emerging from an era of segregation; they were immigrants from the Commonwealth who had faced discrimination on arrival in the UK. Among other things, they sought to quash a repatriation bill, and succeeded.

All this bears remembering, in the light of recent treatment of the Windrush generation – the concerns to which the Booker drew attention are not antique. And it’s worth recalling, too, what Berger actually said. Because you might argue that when he made his acceptance speech, he didn’t just give the prize the greatest public impact it had hitherto enjoyed. He also drew attention to the possibility of a prize that would shed light on the world and welcome its rebels. As the writer David Storey put it, before winning the Booker in 1976, “Prizes tend to be rewarded to the reliable rather than the liabilities, and the liabilities are the people who matter in the end”.

Immediately after Berger’s win, the prize continued that tradition of engagement with the world at large and not just the world of publishing. The archive contains a letter from Mary McCarthy, a judge in 1973, just back in Maine “having been in Washington with Watergate”. And the writer to whom the 1973 prize was given, J. G. Farrell, went on to insult his benefactors as he accepted the prize, admitting that in doing so he was ensuring that “each year the Booker Brothers see their prize wash up a monster more horrid than the last”. All of this, the prize has absorbed. Because its mission is not just to find out who the best writers are; it’s to make available to a wider public their habits of thought.

At the Café Royal on the evening of November 23, 1972, Berger said: “Prizes act as a stimulus. And so the basic cultural value of a prize depends upon what it is a stimulus to. If a prize only stimulates conformity, it merely underwrites success as it is conventionally understood. If it stimulates imaginative independence, it encourages the will to seek alternatives. Or, to put it very simply, it encourages people to question … . My position is not first and foremost a question of politics … the issue is between me and the culture which has formed me”. He wasn’t dismissing the prize or rejecting it; he was giving it a way to be.

What do the judges seek, and how do we seek the judges? The former judge Ruth Rendell pointed out (characteristically, given her chosen genre) that it’s not really a “jury”, because jurors have to decide between innocence and guilt; Man Booker judges have to choose the best. But what does that mean? There is no more specific remit – each set of judges has to make up its own model.

One of the risks of the prize’s being so well-established is what the former chair Fay Weldon warned of when (echoing David Storey) she described “the whole institutionalised tendency to play safe and avoid trouble”. Good books may cause no trouble at all, of course, but – judges have to ask themselves – are we open to them if they do? Another issue was illustrated as long ago as 1987, when Julian Barnes wrote about the prize, after he’d been shortlisted but long before he won it. “The Booker, after 19 years”, he wrote, “is beginning to drive people mad. It drives publishers mad with hope, booksellers mad with greed, judges mad with power, winners mad with pride, and losers (the unsuccessful shortlistees plus every other novelist in the country) mad with envy and disappointment.”

The only thing to do, in the face of these things, is to be fair – to be rigorously welcoming of all possibilities for excellence, regardless of genre or geography, and to welcome dissent if it comes too. The more successful the prize is, the more committed it must be to this aim. It’s not supposed to have a particular profile – except that of good judgement – and it’s not supposed to be bestowed by a particular category of people. The books should dictate the character of the prize, rather than the prize seeking to reward a certain kind of book. The process is a form of inquiry: “What is the best of what’s being written today? How does it differ from what was written yesterday?” And it’s also an offering – or, you might say, the beginning of a conversation: “This is what we think, for now – take a look”. It is the opposite of absolute.

The Man Booker Prize is alone in asking all five of its judges to read all 150-plus of its entries. This is because every novel must stand a chance of finding its ideal reader on the panel. If a group of judges is operating at its best, they will each be drawn to different books but be persuadable about others. The chemistry is in the conversion of a private experience into a communal discussion – a process that is fantastically invigorating to watch.

When Graham Swift won the prize for Last Orders in 1996, he noted that although its impact on a writer’s fortunes in Britain was well documented, he’d had no idea until then “how extensively it is respected abroad”. That has also been its purpose from the outset. The very first year, hundreds of copies of P. H. Newby’s Something To Answer For were sent to Zambia, as well as to Trinidad and Guyana. And now that the Man Booker International Prize rewards novels translated into English, the effects are being felt by writers even in their own countries. When Han Kang and her translator Deborah Smith won the Man Booker International with The Vegetarian, a book that had been published in Korea a decade earlier and sold 20,000 copies in that period, half a million copies of the Korean edition were ordered within a fortnight.

There is one particular strange effect of the judging process. Just as a wedding is almost diametrically opposed to a marriage (the first being a one-off public event and the second being, with any luck, long and private), the small room in which the winner is chosen doesn’t remotely reflect the colossal impact of the decision made there. Judges spend months talking and whittling things down. Eventually, the pressure is upon them; they must choose the best book. Is it the one that looks best to them now, in close-up, after an unprecedented amount of reading? Or is it the one that, when they look up and out into the world, they would most like to press into the hands of the most people? Ideally, the answer to both questions would be the same. But it’s worth bearing in mind, because that’s what happens when they leave the room. They go to dinner, and the book goes everywhere.

It’s a huge responsibility to think of the prize as being global, but there’s no denying that it is. If you look at the books that have been rewarded, they suggest it always was. When, earlier this year, five judges were asked to read all the winning books, and to select a shortlist of five for the “Golden Man Booker Prize” (one for each decade), the books they chose were remarkable in their lack of insularity. V. S. Naipaul’s In A Free State represented the 1970s, Penelope Lively’s Moon Tiger the 80s, Michael Ondaatje’s The English Patient the 90s, Hilary Mantel’s Wolf Hall the 00s and George Saunders’s Lincoln in the Bardo the 10s. Together, these books span the world – India, Africa, the Caribbean, England, America.

In that respect, opening the prize in 2013 to all novels written in English and published in the UK was a statement of the obvious. This alteration is often characterized as “opening the prize up to Americans”, but it’s not actually an addition – it’s an elimination of the premise of citizenship. This means that anyone, of any nationality, writing in English, is now eligible for the Man Booker Prize, as long as their books are published in Britain.

Recently, there have been suggestions that Americans have no place competing in this prize, and – most disconcertingly – that their presence pushes out more marginal voices to which the prize has traditionally drawn attention. These are important considerations, and an ongoing conversation is required in order to be alert to them. As things stand, from the trenches, there are a few things to note. The judges hired since that rule change was made are not remotely biased in favour of Americans, and it’s interesting to see how many famous American writers have been eligible but not longlisted in that time: Donna Tartt, Don DeLillo, Jonathan Lethem, Jonathan Franzen, Jonathan Safran Foer – none of the Jonathans, in fact, have made the cut. And marginal voices can have American passports too: Paul Beatty was not well known on either side of the Atlantic when his dazzlingly subversive novel The Sellout won in 2016. More importantly, the fundamental position should be one of confidence: British and Irish and Commonwealth writers can of course be the best in the world.

In the closing lines of his Nobel lecture, given last December, Kazuo Ishiguro made an appeal that the Man Booker Prize might usefully adopt as a partial manifesto. “It’s hard to put the whole world to rights”, he said, “but let us at least think about how we can prepare our own small corner of it, this corner of ‘literature’, where we read, write, publish, recommend, denounce and give awards to books. If we are to play an important role in this uncertain future, if we are to get the best from the writers of today and tomorrow, I believe we must become more diverse.”

He meant this, he said, in two senses:

“First, we must widen our common literary world to include many more voices from beyond our comfort zones of the elite first world cultures … . Second: we must take great care not to set too narrowly or conservatively our definitions of what constitutes good literature. The next generation will come with all sorts of new, sometimes bewildering ways to tell important and wonderful stories. We must keep our minds open to them, especially regarding genre and form, so that we can nurture and celebrate the best of them.”

George Saunders, who won the Booker last year with a polyphonic novel told literally from the ground up, said recently that because he grew up in working-class Chicago, he didn’t feel he could “come in through the front door of literature”. Instead, he entered “through the basement”. There is something especially pleasing about the idea that the Man Booker Prize can reward any writer, whichever door she or he comes through. It is, I think, what was always meant. As one former chair put it, elegantly overturning ingrained industry assumptions: “Literature is not a club. It’s a game – and anyone can play it”.