Lifting the lid on spoilers

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Image caption Some Bake Off fans were aggrieved to learn of the outcome of episode three before it was broadcast

Non-spoiler alert! There are no spoilers in this article (hopefully).

Great British Bake Off star Mary Berry accidentally revealed the result of the most recent episode before it had been broadcast - to the consternation of fans of the show.

As highlighted by the baking judge's inadvertent revelation during an interview with Chris Evans, spoilers are a common hazard for TV-watchers.

Catch-up services and recordable devices mean many don't want to know the result or ending even after it has been broadcast, which renders the social media sites swarming with spoilsports a complete no-go zone.

To be fair, Berry is not the first to be guilty of such a gaffe - and she won't be the last.

From TV to films, books to theatre, if it has a dramatic ending it can be spoiled.

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Image caption The Sixth Sense was a film about a boy who could see dead people and became well known for a big twist

One common complaint among cinema-goers is that films can be ruined by their own advertising, according to Dr Keith Johnston, a senior lecturer in film and TV at the University of East Anglia's media school.

His team surveyed more than 500 film fans and learned there is a fine balance to be found, with a tipping point where teasing trailers turn into too much information.

"There are some who think trailers are too revelatory and show you too much," he said, "but then some say they want to see lots of the narrative, the characters and the world they are in to help them decide whether or not they want to see it.

"It's only after people have seen the film that they can know if they knew too much of it from the trailer."

Dr Johnston said comedies are usually the most criticised; dramatic moments can be seen in a trailer and then in the film without complaint because the context affects the viewer's enjoyment, but the punch line to a joke lacks the same impact when seen a second time.

Some films, such as The Sixth Sense, are famous for a big twist which, if it were known beforehand, would ruin people's enjoyment of the movie.

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Image caption Director Alfred Hitchcock understood the risk of the spoiler and asked his audience to keep the plot of Psycho a secret

But Dr Johnston said any good film must have more to it than one big twist and should have enough other elements in it to entertain.

Legendary director Alfred Hitchcock realised the importance of keeping the story a surprise, urging viewers of Psycho not to reveal the ending as "it's the only one we've got".

He even bought up all copies of Robert Bloch book on which the 1960 film was based to limit the chance of people learning the film's cracking twists.

Whodunnits rely on the ending being kept secret, and nowhere is this better known than with Agatha Christie's long-running murder mystery play, The Mousetrap.

At the end of the play and after the applause has died down, the lead actor makes a direct appeal to the audience, a tradition started by Richard Attenborough on a stage in Nottingham more than 63 years ago.

Theatre-goers are told they are now a part of the crime and are asked to keep the secret of "who done it" locked in their hearts.

Image caption Richard Attenborough was the first actor to appeal directly to the Mousetrap audience to keep the identity of the killer secret

And the audience members are happy to comply, according to the play's producer Sir Stephen Waley-Cohen.

"It is an extraordinarily well-kept secret because people love to keep a secret, it makes them feel a part of something," he said.

"Most people have a great time watching the story and trying to beat Agatha Christie by working out who has done it, they want their friends to also have a great time - people are considerate.

"Of course there are a few who are disaffected, ill-willed or just plain stupid and do not think about what they are saying, but we really have not come across many people like that."

Christie was upset when reviewers revealed plot details and in 2010 her grandson, Matthew Prichard, complained when Wikipedia included the ending of The Mousetrap on its page about the play.

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Image caption Agatha Christie's The Mousetrap is a classic murder mystery play

Spoilers are infuriating for fans, says regular theatre-goer and arts PR expert Michael Eppy.

"Think of Game of Thrones, you can't even mention it without four people in earshot putting their fingers in their ears and shouting 'la la la la la'.

"I do think people are considerate generally, but it only takes one blabbermouth to ruin hours of build-up and anticipation.

"It can make you want to cause physical harm to the offender."

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Image caption The Mousetrap has been at St Martin's theatre in London for 39 years and is claimed to be the longest-running show in the world

But there is a clear dilemma for professionals whose job it is to discuss the latest releases.

Avoiding spoilers, or at the very least acknowledging they may be an issue, is a basic requirement, says Dymphna Flynn, a producer on Radio 4's Front Row and Bookclub.

And there is no time limit on a secret, she claims.

"We had David Nicholls on to talk about his book One Day. It had sold 5m copies and been out for years so some people said it would be ridiculous not to discuss the ending.

"But he didn't want to and we always think of the new reader who hasn't read it yet, no matter how old the book.

Image caption Author David Nicholls did not want the ending of his book One Day revealed when he appeared on Radio 4's Bookclub

"We got around it by discussing it in very general terms so that people who had read the book would get the answer they wanted without ruining it for others yet to read it.

"It is one of the basic questions we ask the author of any book with a big reveal, almost as basic as what time are you going to turn up to the recording, that consideration is part of the programmes' furniture."

You have now reached the end of this article, please don't tell others how it ends.

By the way, the murderer is...

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