Sometimes these statements seem intended to provide a veneer of respectability beyond mere "fiction", other times they are more informational, and in the case of more recent events may, in their hedging, might be worded to provide some legal protection.

Dramatising real-life events in a movie is always a challenge. Film isn't the best medium for covering long periods of time. Dealing with all the elements and complexities of real life - not to mention the basic facts of whatever story is being told - is hard enough in, say, a lengthy book: a movie can only highlight, condense and endeavour to capture the essence of its subject matter. And that's assuming the filmmakers can find, and care about, the truth in the first place.

One way of dealing with the difficulties is to have composite or fictional characters. Bombshell does this. John Lithgow plays real Fox News boss Roger Ailes and Charlize Theron and Nicole Kidman plays respectively, real-life Fox News employees Megyn Kelly and Gretchen Carlsen.

But Margot Robbie as Kayla Pospisil, an ambitious evangelical Christian, and Kate McKinnon as Jess Carr, a lesbian Hilary Clinton supporter who works for Bill O'Reilly, are not real. They might be taken to represent some of the other people at Fox.

Kelly and others depicted have said some elements are entirely made up while others are true or at least accurately represent their feelings. And some critics have said the film underplays Kelly's less admirable qualities to create a goodies and baddies narrative. Everybody has an agenda, of course.

The need for conflict in drama means it can often be confected. A Beautiful Day in the Neighbourhood, in which a cynical journalist is sent to interview the beloved American children's-show host Fred Rogers, was based on an Esquire profile by Tom Junod.

His interactions with Rogers seem quite accurately depicted but a fictional subplot depicting the journalist's heavy conflict with his father led Junod to request the character's name be changed.

Screenwriter William Goldman sought the advice of Watergate journalist Bob Woodward when adapting All the President's Men into a workable script. But he sometimes resorted to fiction: the film's most memorable line, Deep Throat's advice to "Follow the money", is Goldman's creation.

Goldman also prefaced Butch Cassidy and the Sundance Kid with the facetious title, "Most of what follows is true": when dealing with legendary outlaws, separating fact from fiction is hard.

So is not glamorising them, apparently: casting Paul Newman and Robert Redford made this nigh on impossible. The recent True History of the Kelly Gang - "None of what follows is true" was the disclaimer - was less hagiographic but, being based on a novel, less historical than many accounts.

Some movies like Braveheart are riddled with historical untruths, intentionally or otherwise. And living people can exert control (were Queen's members really as squeaky-clean as Bohemian Rhapsody depicts them?)

The lesson? Don't believe everything you see and hear - in movies or in life.