An academic claims to have solved one of television's most enduring questions - just why are the Daleks so scary?
Dr Robin Bunce said the fear inspired by the creatures, who have sent generations of children scurrying behind sofas, is nothing to do with their robotic cries of "exterminate" or their relentless attempts to conquer the world, but because we are worried we might become like them.
The Cambridge University academic said: "The reason the Daleks are evil is because we recognise that they were once better. They are the nightmare future we dread."
Dr Bunce based his research on the original storyline which first introduced the creatures to the show in 1963.
It told viewers the Daleks had retreated into their metal shells after a devastating war and slowly lost their emotions, becoming more like machines than living and breathing creatures.
Dr Bunce said: "According to their back story, once they were capable of genuine emotion and real moral good.
"Now they are sexless, heartless brains, shut up in machines incapable of intimacy, who have forgotten what it means to laugh and no longer think of themselves as individuals.
"We recognise the Daleks as evil because they have lost all that we hold most dear."
The Daleks have made regular appearances in the long-running science fiction series, with the latest being last year when they turned up in an episode set in Blitz-torn London.
They were voted the scariest villains in the history of Doctor Who in a poll of 21,000 fans in 2007.