This is the year of the departed. On July 21, fateful day, we learn whether Harry Potter lives or dies. Two deaths are predicted by his creator, J.K.Rowling, but will one of them be Harry’s? Even as we wait, breathless with anticipation, Inspector Rebus is shuffling off into an uncertain future; Ian Rankin is writing his world-weary detective out of the script. To die, to sleep? Only the author knows. But Rebus, it seems, has solved his last case. From now on, we will have to be content with Precious Ramotswe, Botswana’s indefatigable lady detective, still ticking over at the end of Alexander McCall Smith’s latest volume, like the engines her husband repairs at the Tlokweng Road Speedy Motors. The well-oiled storyline runs smoothly on — “like life”, she remarks contentedly. But for how long?

There is nothing to match the tyranny of a long-running hero — except perhaps for the tyranny of the insatiable reader. There comes a time when, like the guests who have overstayed their welcome, principal characters have to be asked to leave. By that point, however, they have taken on a life of their own, and the decision about whether the exit should be terminal or not may well be decided by others. Conan Doyle became exasperated by the success of Sherlock Holmes — he was keeping the author from more serious historical work; he had become a bore. “I weary of his name,” said Conan Doyle. And so, in The Adventure of the Final Problem, Holmes found himself on the Reichenbach Falls, locked in combat with his age-old enemy, Professor Moriarty, and there, at the stroke of a pen, they both tumbled into the foaming torrent far below.

Unknown to Conan Doyle at the time, however, Holmes had survived. Or rather, the 20,000 outraged readers who cancelled their subscription to the Strand magazine as a result of the great detective’s death ensured that he did, in fact, albeit belatedly, break his fall by grasping a tussock of grass on his way down, crawl back up the cliff, and then reappear eight years later in The Hound of the Baskervilles, bringing with him 30,000 eager new readers. Improbable? Of course. But, as Holmes himself was wont to point out: “However often have I said to you that, when you have eliminated the impossible, whatever remains, however improbable, must be the truth.”

Of course, the reader may take a different view altogether, and indicate that the time has come for a well-known character to leave the novel. Mrs Proudie, the bishop’s wife in the Barchester chronicles, is one of Anthony Trollope’s most formidable creations — “a tyrant, a bully, a would-be priestess, a very vulgar woman”, he called her himself. There was no particular reason for her to go, however, until Trollope overheard two cronies in his club complaining about the number of times Mrs Proudie kept reappearing. Forthwith, he decided to kill her off. Contemplating her corpse in The Last Chronicle of Barset, her husband experiences a mixture of pain and relief, with the latter the stronger of the two emotions: “He was now his own master . . . the tyrant was gone and he was free.” He was undoubtedly expressing the feelings of Trollope himself.

Agatha Christie took longer to make up her mind. Hercule Poirot, the Belgian detective, brought out of retirement in 1920 to appear in The Mysterious Affair at Styles, was still solving crimes 40 years later, despite the author having long since tired of him. Unable to dispose of him publicly, Christie invented a fictional lady detective, Ariadne Oliver, through whom she expressed her feelings. Ariadne had created her own detective, whom she heartily disliked and made no bones about disparaging. It was Christie’s way of venting her feelings about Poirot. Secretly, she had him poisoned. In Curtain, written during the Blitz, Poirot meets his end at Styles, the house where he had begun his fictional career. Christie had meant to have the novel published posthumously, but it came out in 1975, a year before her death.

There is a lesson here for Rankin and Rowling, and indeed for every inventor of a successful character. Such is the popular appetite for fictional heroes that they can acquire a longevity and an instinct for survival that often takes their author by surprise. The reality they convey may be stronger, and certainly more attractive, than the monochrome version which, for many readers, passes for ordinary life. This psychological transference accounts not only for the popularity of TV soap operas but for the fascination with minor celebrities, the success of Hello! magazine, and the obsession with reality television shows. The viewer or reader ceases to worry about which is real and which is invented, because the distinction between a soap star, who is fictional, and a character like Elizabeth Hurley, who is a real person but comes across in glossy, fictional form, becomes ever harder to define. Thus, we love Shilpa Shetty, the racially abused Indian actress, and hate Jade Goody, who insulted her, in much the same way as we warm to John Rebus and shiver at Lord Voldemort.

So when, eventually, Rebus collects his P60, and Harry Potter confronts his final fate, we should not be surprised if there is widespread mourning across the land, and a clamour for them to return. Enormous pressure will be put on both authors for just one more sequel, one final opportunity to share the grime of St Leonard’s police station, or the mystery of the Hogwarts School of Witchcraft. They must resist it. A character who returns is never quite the same as the one who left. A clean break is better for all concerned.

Not that it will be easy — and already, Rowling is mourning her loss. On her website she quotes Dickens: “It would concern the reader little to know how sorrowfully the pen is laid down . . .” On the contrary, we feel the pain already.

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