In April 1944, when he was 19 years old, Rudolf Vrba did something truly extraordinary. With his fellow prisoner Alfréd Wetzler, this son of a sawmill owner from provincial Slovakia became the first Jew to break out of Auschwitz. And he did it to warn the world.

The report the two escapees would compile, detailing the horrific minutiae of life inside the most notorious of the Nazi death camps, would, through a succession of international diplomatic efforts, save an estimated 200,000 Jewish lives. To my mind it represents one of the greatest single achievements of the Second World War — one that should make Vrba stand alongside Anne Frank, Oskar Schindler and Primo Levi, those whose stories shape our understanding of the Holocaust.

And yet, when the Vrba-Wetzler report reached, by a secret and circuitous journey, those in power — eventually ending up on the desks of Winston Churchill, Franklin Roosevelt and Pope Pius XII — the immediate result was neither a loud outcry nor decisive action but rather silence and paralysis.

The report the two escapees would compile, detailing the horrific minutiae of life inside the most notorious of the Nazi death camps, would save an estimated 200,000 Jewish lives.

Part of the explanation was simple prejudice. Note the reaction in London when the full text reached the Foreign Office. “Although a usual Jewish exaggeration is to be taken into account,” wrote one official, Ian Henderson, “these statements are dreadful.” Less than a fortnight later a colleague in the same department would write: “In my opinion a disproportionate amount of the time of the office is wasted on dealing with these wailing Jews.”

Washington was not much better. The report was passed from department to department within the US government, at a lethargic pace, but a copy eventually reached Yank, a US army journal. It wanted to run a feature on Nazi war crimes but declined to use the material Fred and Rudi had brought out: the magazine found it “too Semitic” and requested a “less Jewish account”.

Sometimes the objection to action was practical. Various Jewish officials had attached a plea to the text of the report, urging the Allies to bomb the railway tracks to Auschwitz. Churchill was sufficiently moved that he sent a scribbled note to his foreign secretary, Anthony Eden: “Get anything out of the air force you can and invoke me if necessary.” But the minister in charge of the RAF, Archibald Sinclair, said no, insisting that “interrupting the railways” was “out of our power” and that the RAF could not do “anything of the kind”. Eden did not press the matter.

“In my opinion a disproportionate amount of the time of the office is wasted on dealing with these wailing Jews.”

But the escapees’ testimony encountered a more fundamental obstacle than prejudice or practicalities. It ran into a wall of disbelief.

That was something Vrba himself had not prepared for or even imagined. As a prisoner in Auschwitz for the best part of two years — an unusually long time, given that the life expectancy of most arrivals was measured in hours — he became convinced that this factory of death was able to function only because it remained a secret. Once the outside world knew of the horrors committed there, once the word was out, the killing machine would, he felt sure, be broken.

And so he and Wetzler, from the same small Slovak town of Trnava, plotted an escape, hiding in a hole in the ground within the camp for three days and nights as thousands of SS men — and their dogs — searched for them round the clock. For 80 hours they lay still, barely moving, until eventually the SS followed their standard, unvarying protocol — predictability being the Nazis’ fatal flaw — and called off the search on the presumption that the two men had somehow got away. That was the cue for Vrba and Wetzler to emerge from their hiding place and, in the dead of night, inch their way to the outer fence and out.

From there they trekked through occupied Poland, with no compass and no map — taking care to walk only at night, crossing rivers, mountains and marshland, dodging the double threat of the SS and local collaborators — until, 11 days later, they reached Slovakia. There, and in hiding, they made contact with the remnant Jewish community and wrote their forensically detailed 32-page report, the first full account of the murder center that was, by then, working 24 hours a day to eradicate the Jews of Europe.

Powering them was the faith that every whistleblower, every revealer of terrible secrets, shares: the belief that once people know of a shocking truth previously hidden, they will rise up — that the act of revelation will prompt an outraged world to demand that the horror be stopped.

But that faith proved to be misplaced. It missed something deeply troubling about human nature: that the bearers of terrifying news are not always believed.

In hiding, Rudolf Vrba and Alfréd Wetzler wrote their forensically detailed 32-page report, the first full account of the murder center that was, by then, working 24 hours a day to eradicate the Jews of Europe.

Witness the way Jewish leaders in Hungary reacted when the report reached them within days of its completion. They were the audience Vrba most wanted to address: he was desperate to warn the Jews of Hungary what fate awaited them if they boarded the trains that would take them to Auschwitz. In the spring of 1944 they were the last Jews of Europe, the last Jewish community left untouched by the Nazis’ “final solution to the Jewish problem”.

Vrba understood that they were hardly in any position to mount a revolt, but he believed that if only they could read his report, if only they could be told what he knew, then they might at least refuse to go quietly and obediently to their deaths. That refusal alone, and the chaos that would ensue, would, Rudi was certain, be enough to slow or even derail the Nazi project of genocide.

But the Jewish Council in Budapest could not believe what Vrba and Wetzler were telling it. The council’s president, Samu Stern, wondered if the report was perhaps the product of the fertile imagination of two rash young men. Surely, he and his colleagues feared, it would be reckless to distribute such an alarmist text: it would cause panic and expose those who had published it to the charge of spreading false information.

So the report stayed locked away, even through May, June and early July 1944: a 56-day period in which 437,402 Jews were transported from the Hungarian countryside, crammed into 147 trains, to Auschwitz, where almost all of them would be gassed on arrival. Till his dying day, Vrba was convinced that if his testimony had been distributed, thousands, maybe even hundreds of thousands, of those lives could have been saved.

For all that, word did reach some of Hungary’s Jews. But even then the first reaction was disbelief. One young man, György Klein, then a teenager just like Vrba, saw a copy and went immediately to warn his uncle. Instead of gathering up his things and rushing for safety, the older man became so angry that he came close to hitting his nephew. “His face got red; he shook his head and raised his voice,” Klein would recall many years later. How could György believe such nonsense? It was unthinkable, impossible.

Till his dying day, Vrba was convinced that if his testimony had been distributed, thousands, maybe even hundreds of thousands, of lives could have been saved.

Even on the one occasion when Jews packed into the trains to Auschwitz were given the most authoritative warning imaginable, they still struggled to believe what they were hearing. Two more Jews escaped after Vrba and Wetzler, and their testimony was added to the report. Tragically, one of those subsequent escapees, Czesław Mordowicz, was captured and sent back to the death camp. Inside the cattle truck he warned his fellow Jews what was in store for them at the end of the line. He had been there: he knew.

“Listen,” he pleaded, “you are going to your death.” Mordowicz urged the people jammed into the wagon to join him and jump off the moving train. Instead they began shouting, banging on the doors and calling the German guards. They attacked Mordowicz and beat him so badly, he was all but incapacitated. He never did leap off that train, but ended up back in Birkenau. All because he had given a warning that the warned could not believe and did not want to hear.

It was while I was learning all this, working on the story of Rudolf Vrba, that I saw the apocalyptic satire Don’t Look Up. It rests on the notion that when someone comes to warn of an imminent disaster — say, the climate crisis — people will find almost any excuse to shake their heads or look the other way. The film resonated because I knew of the response that had greeted the 19-year-old Vrba and his dispatch, written from the hell on earth that was Auschwitz. I have the same reaction now when I read of those Russians who refuse to accept the word of their own sons and daughters about their country’s invasion of Ukraine.

Vrba would go on to build a new life for himself after the war, becoming a biochemist in Czechoslovakia, Israel, Britain and finally Canada. He died in 2006, aged 81, leaving behind the story of an extraordinary act of heroism. There are many lessons to learn from it, but one of them is painful to accept, and it is this. People can have all the information they need, but before they will act, they have to do something that can be very hard, especially when that information is terrifying: they have to believe it.

Jonathan Freedland is a columnist for the Guardian and a presenter on BBC Radio 4. His book, The Escape Artist will be published by Harper on October 18