Natalie Haynes: It's ludicrous, but we want it to be true

London Zoo is currently refurbishing a large area that backs on to Regent's Park. Where once there were camels and a pygmy hippo, now there are diggers. Recently, a sign was added, explaining that they were building the new tiger enclosure there. "Ooh, tigers next to the park," I thought, as I strode past on my way to work. Then, a moment later, "Wait, tigers next to the park?"

Luckily, we've never had to deal with anything more alarming than a red panda escaping from London Zoo, which clearly locks up its big cats with care. As does Colchester Zoo, for the Essex lion has, like every other big cat on the loose, vanished as completely as the Loch Ness Monster and the Beast of Bodmin Moor. He is probably a Maine Coon cat which lives nearby.

Escaped big cats are the urban myth of the countryside: the tales abound because so many of us want them to be true. It's always big cats caught in a blurry photograph, never zebras or wolves, which are surely just as likely to have escaped from a private zoo as a lion. Even now, with the search called off for lack of evidence, one newspaper poll suggests that more than a third of us think the Essex lion is real.

The desire to believe something which is manifestly false is extremely powerful. The brilliant new documentary, The Imposter, illustrates this beautifully: it tells the story of a blond, blue-eyed boy who disappeared in Texas aged 14. Three years later, a dark-haired, brown-eyed man in Spain claimed to be the missing child. I won't spoil it for you, only urge you to go and see what people are capable of believing when they want it to be true.

I suspect the same tendency is at work with the current spate of Twitter deaths: our craving for a good story trumps our need for evidence. Russell Brand has had to debunk rumours of his death this week. One documentary about addiction, and he's shunted towards the great beyond. It seems our love of a good story requires a big finale. But reports of his death, much like the life of the Essex lion, are exaggerated.