In 2016 I finally managed to publish a book that I had been wanting to write for more than 30 years. “I have only two criteria for a novel,” Patricia Highsmith once wrote. “It must have a definite idea behind it, precise and evident; it must be readable, so readable the reader doesn’t want to put it down even once. I don’t know but that I set the second criterion higher than the first.”

It’s a high ambition, easier to state than to achieve. But that, at any rate, is what I tried to do in Munich: to make the four days of complicated diplomatic maneuvering in September 1938, when Europe teetered on the edge of war, as readable as possible; and to do so with the “definite … precise and evident” idea of painting a more sympathetic portrait of Neville Chamberlain, probably still the most reviled prime minister in British history.

In an attempt to avert war, Prime Minister Neville Chamberlain leaves London for a meeting in Munich with Adolf Hitler, September 1938.

I am not alone in believing that Chamberlain has had a rough deal from posterity. The iconoclastic Sunday Times critic AA Gill, three months before his death, selected Chamberlain as his hero for Radio 4’s Great Lives series: “The desire for peace is never a bad desire,” he said. “One of the things that attracts me about Chamberlain and about appeasement is that [the war] has made it almost impossible for any other politician to come forward with the idea of appeasement. You can see it affecting, say, the Iraq war, where the idea of saying, ‘We have to go in and somehow appease Saddam Hussein’ — someone just had to stand up and say, ‘Well, you’re just Neville Chamberlain again,’ and that was it. And we are now living with the consequences.”

In conflict after conflict since 1945 — Suez, Vietnam, the Falklands, the Gulf, Afghanistan, Iraq, Libya, Syria — opponents of military action have invariably had the slurs of “Munich”, “appeasement” and “Chamberlain” flung in their faces, as if they alone were sufficient to end the argument. That was why I wanted to write the book. The issues and dilemmas exposed in September 1938 reverberate to this day.

Of course, with hindsight, we know that Chamberlain’s policy failed. He admitted it himself after declaring war on Germany: “Everything I have worked for, everything that I have hoped for, everything that I have believed in during my public life, has crashed into ruins.” But that is not the same as saying it was wrong at least to try to avert a war that left more than 50 million dead.

The great justification for writing historical fiction is that you can, by getting inside the heads of your characters, throw a series of emotional switches that will engage the reader’s sympathy with a power that is denied to historians.

Extra! Extra! The front page of the Daily Express on September 17, 1938, reporting on the prime minister’s peace talks with Hitler.

I thought that if I could try to see the story of Munich through Chamberlain’s eyes — by describing the military unpreparedness he had inherited as prime minister (despite the fact that the UK, under his leadership, eventually was spending half of all tax revenue on rearmament); the fear (misplaced as it turned out, but universal at the time) that London would be all but obliterated by bombing with high explosives and poison gas; above all the sense that Europe was once again sliding into a murderous war less than 20 years after the last (which had cost nearly 900,000 British lives) — if I could do all that, I could perhaps show him as a tragic hero rather than merely the gullible old fool of popular myth.

I started researching Munich in the mid-1980s. For a BBC documentary in 1988 to mark the 50th anniversary of the conference I interviewed eyewitnesses, including Chamberlain’s daughter, Dorothy, and his parliamentary private secretary, Alec Douglas-Home. I thought of casting the novel in the form of a memoir by Chamberlain written just before his death, but that struck me as too dry and limiting. Next I had the idea of inventing a young private secretary who would fly with Chamberlain to the Munich conference — but again it didn’t seem to offer a broad enough perspective.

The issues and dilemmas exposed in September 1938 reverberate to this day.

Then in 2007 the German historian Joachim Fest — the ghostwriter of the memoirs of Hitler’s armaments minister, Albert Speer — published his diary of their collaboration. Among the material that never made it into the book was an account of Hitler’s reaction to the events of September 1938: “Speer told us that, after the Munich conference in 1938, Hitler was in a bad mood for many days and, contrary to habit, vented his anger in petty matters.”

Alex Jennings as the prime minister’s adviser Sir Horace Wilson, and Irons as Chamberlain.

Of course no one dared ask him for the reasons, and he himself said nothing … It gradually leaked out that because of the softness of the other powers, Hitler felt he had been swindled out of a real victory. A fortnight later he said at a small gathering that he had been cheated, and not only by the cowardice of the British and the French. The vacillating Germans had allowed themselves to be unceremoniously duped. “Our dear Germans!” he added bitterly. “By that Chamberlain of all people!”

The Churchillian interpretation of Munich — that Hitler cleverly managed by threats and bluff to obtain all that he wanted without having to fire a shot — is simply false. The German dictator wanted a war in 1938 and to the end of his life regarded himself as having been outmaneuvered by Chamberlain. Looking back ruefully from the bunker in February 1945 he lamented: “We ought to have gone to war in 1938 … September 1938 would have been the most favorable date.”

Now, at last, I realized that to tell the full story of Munich I would need to see it from the German angle as well as the British. I gave my Downing Street private secretary a name — Hugh Legat — and crucially I gave him a German friend from his student days at Oxford: Paul von Hartmann, loosely based on Adam von Trott, a member of the embryonic anti-Hitler resistance in the German Foreign Office. The two young men travel with their respective leaders to Munich and in the novel’s central scene present Chamberlain with proof that Hitler is bent on a war of conquest.

Hitler and Chamberlain at the Hotel Dreesen in Bad Godesberg, one of two trips the prime minister made to Germany during negotiations for the Munich Agreement.

As it happened, on the day in June 2016 when I wrote that scene I also had lunch with Jeremy Irons to discuss a different project. Looking at him across the table, I realized — improbable though it seemed — that he bore a striking resemblance to Chamberlain, albeit in a vastly more handsome form. I mentioned the novel, sent it to him, and a week later he expressed interest in playing the part.

I could perhaps show him as a tragic hero rather than merely the gullible old fool of popular myth.

And now here he is, even more improbably — for these things almost never work out in practice — starring in the Netflix adaptation Munich: The Edge of War. I am not so vain or naïveas to believe that 80 years of denigration will be overturned by one performance or one movie. Trying to make a deal with Hitler was worth a try, bought us the time to rearm, and certainly gave us the moral determination not to enter peace talks in 1940 (a decision in which Chamberlain’s voice was crucial). But it was unavoidably shameful, and in its own terms, a complete failure.

Still, it is a mark of maturity to be able to hold two competing views in one’s head at the same time: that Churchill was vital to the defeat of Germany, and so, in a different way, was Neville Chamberlain. If people come away from the film both entertained and with a more nuanced view of Munich, then my long obsession will have been worthwhile.

Robert Harris is a novelist and former journalist based in Berkshire, U.K. His most recent book, Munich, has been adapted into a film now streaming on Netflix