'Based on a true story" ...."Inspired by actual events"...automatically these words on the opening credits lend an extra frisson to a film or a TV series. But to arrive at some understanding of this fiendishly tricky subject, we should probably start with a book, A Million Little Pieces, by James Frey.
It was a book about alcohol addiction which was offered to various publishers as a work of fiction, and rejected. It was eventually published as "non-fiction" and it sold millions, driven by an endorsement from Oprah - who then had to haul the author back to berate him like a bold boy for misleading her and the American people, when it emerged that several parts of the book were exaggerated or just invented.
Frey was in no position to argue, but I would argue on his behalf that he was to some extent the victim of an industry which had lost its confidence, which was dumbing down. That he had written a powerful novel, but that it needed this fake stamp of authenticity - "it all really happened, you know" - to get it on Oprah.
So I think there is more to this "based on a true story" racket than issues of artistic licence, and of where exactly you draw the line between fiction and non-fiction and all that. There is also at times an element of cynicism, of declaring that a story is true and then making it up anyway, a bit like the events recalled in Charlie when they were putting bogus stamps on the beef to Iraq.
Charlie itself was not motivated by any of that dark stuff, but the arguments that blew up around it are being replicated all over the free world - The Imitation Game, the biopic of the code-breaking genius Alan Turing, played by Benedict Cumberbatch, is accused of taking horrible liberties, of misrepresenting really important parts of Turing's story, and of actually making the man more unloveable than he was.
Last week the BBC had its own version of the Charlie debate in relation to the opening episode of the six-part adaptation of Hilary Mantel's novel Wolf Hall. On Newsnight they tried to tease out the rights and wrongs of a sumptuous TV drama which is based on a work of literary fiction which itself is based on various works of English history involving Henry the Eighth and Thomas Cromwell and Cardinal Wolsey, history-writing itself being a creative endeavour and in some cases a farrago of lies, influenced by source materials which may be of dubious provenance.
With Wolf Hall we are made to wonder if even a production with the most impeccable standards and values can be regarded as a form of cheating. For those who bought the Mantel book when it won the Man Booker Prize, but who have never got around to reading it, does watching it on the telly absolve them of their guilt? And by the way, does anybody ever read those books anyway?
BBC2 also had The Eichmann Show, "based on the true story" of how a producer and a blacklisted director filmed the trial in 1961 of Adolf Eichmann, which became the first ever global TV documentary series.
Perhaps, at the time, those guys too were getting tired of people just making things up.
So given all the complications which naturally arise in this shadowland between what is true and what is half-true and what is not even vaguely true, perhaps the odd thing about Charlie was that it chose the option that was easily the most target-rich.
By going for this broad sweep in which a multitude of characters dropped in and dropped out, with events piled on events over a long period of time, it was humanly impossible to avoid all those boring discussions about whether Albert Reynolds was given a fair shake, or whether Des O'Malley would ever have done that thing with the sword.
I maintain that Haughey's Hot Press interview with John Waters should have been the true story on which the drama was based. You'd still have the magnetism of Aidan Gillen and the excellence of the production, without the constant feeling that at any moment forty Fianna Failers are about to burst through the walls roaring.
It can still be done of course, "based on an original idea", which I will release for the usual percentage.