Years ago, I sold a book about Eva Perón to a Hollywood producer. At a screening of the five-hour television version, I nodded off after an hour, waking to see the conning tower of a German submarine, from which a man wearing a beard and an eyepatch emerged. This left me perplexed because I had expended many pages establishing that, contrary to the myths, Eva and Juan Perón hadn't been the recipients of Nazi gold. However, the producer affably dismissed my objections. "It could have happened even it didn't," he said.
The fictionalising of true stories is fascinating because there seem to be no discernible rules for directors to follow. The best films about real people frequently contain many inventions that would be less than pardonable in biography or journalism, while the most high-minded, literally faithful films can be the least successful. Sometimes, the most unexpected insights occur in otherwise vulgarly inept and platitudinous films.
And that, I suppose, is why I am willing to waste time on the lowliest, most crass biopic. To Steven Soderbergh's credit, his Che doesn't succumb to kitsch, but in its scrupulous adherence to the detail of Che's revolutionary career, it is numbingly dull. After two hours of dense beards, photographed in pseudo-documentary half-light, I would have given much for an eyepatch or, indeed, any other conspicuous sign that this film was made for a living audience.
In recent weeks, there have been a slew of films telling "real" stories. We've had the life of George W Bush, the nihilistic career of the Baader Meinhof gang, and Bobby Sands's martyrdom through starvation. Then there is Valkyrie, in which Tom Cruise plays Claus von Stauffenberg, who led an unsuccessful plot against Hitler in 1944.
The biopic has a long, aesthetically dubious pedigree. The dangers lie in what the New Yorker critic Pauline Kael called the importation of advertising or Hollywood values - clearly discernible goodies and baddies. We're required to empathise with all protagonists, even when their cause is dubious.
You see this in The Reader (based on a German novel, which is loosely based on a real-life case). Here, Kate Winslet is on parade as a German concentration camp guard who can't read. This is a film based on a truly bad German bestselling book, both muddled and evasive, and the film isn't any better. We are asked to feel that the character played by Winslet is somehow doomed to become a concentration camp guard because she is illiterate. We should even feel sorry for her. Truthfulness has been sacrificed here in the quest for a nice character, with whose plight everyone will identify. But audiences are able to see through this stratagem.
What liberties can be taken with facts in the pursuit of fictional art? Are there any limits to plundering reality? At a recent NFT masterclass, Peter Morgan, screenwriter of The Deal, The Queen and Frost/Nixon, made a distinction between truth and accuracy. Accuracy, he suggested, was for historians, and everyone knew that there was no real truth in history, which consisted of conflicting reports of what happened. But Morgan also laid claim to the right to make characters more sympathetic. If he didn't do this, audiences wouldn't stay the course.
His confidence that real things can be used to any dramatic purpose he chooses is admirable. But it does depend on the audience sharing in the illusion and the fact that Morgan is also a gifted dramatist, capable of creating characters from real people, undoubtedly helps. We do know that the real Queen can't possibly be as charming as Helen Mirren. Why should we mind? Those of us who don't detest David Frost or Tony Blair will warm to see them depicted as the national type of bumbler, triumphing over ineptitude.
With the darker, less familiar material of The Last King of Scotland, based on Giles Foden's book, however, something was lost in adaptation. You have to look at Barbet Schroeder's famous documentary, with the scene in which he threatens a member of his cabinet with death (later the man is fished out of a river, chewed to death by crocodiles) to see the psychopath in Idi Amin.
Should scriptwriters tamper with the detail of the lives of real people? The answer is that they must do if they are to keep us entertained. None the less, it is possible to make good films within such limitations.
Schindler's List remains Spielberg's finest effort, though most would agree that it was too kind to the real Oskar Schindler, exaggerating the scale of his achievement and tidying up some of the less attractive aspects of his character. But sometimes a film comes along that transcends the limitations of biopics. It is possible to be truthful without boring audiences, though there are few such masterpieces. I'd place the remarkable Downfall, set in Hitler's bunker, within this category. No one will ever match Bruno Ganz's rendering of Hitler's rages or show how monstrous life in underground Berlin, with death nearby, must have been in 1945.
Hunger, too, fully achieves this ambition, in its horrifying recreation of the rituals of the Maze prison and the brutality of all participants, though many will find it difficult to watch Sands's drawn-out, painful death without flinching.
While waiting for the next masterpiece, I intend to indulge my addiction to fact promiscuously mixed with fiction. I'll be watching Tom Cruise make a better Nazi of Claus von Stauffenberg than the man deserves. At least, in the first impression, he doesn't seem to be falling for self-parodying kitsch. The eyepatch he sports is historically accurate. Von Stauffenberg wore one too.
·Nick Fraser is editor of BBC4's Storyville