A study of some of the most successful people in British history has found that only one - Henry VIII - was a psychopath.
Professor Kevin Dutton assessed ten people regarded as among Britain's greatest to determine how psychopathic they were.
He found that Henry VIII was in the same category as dangerous criminals like Ian Brady or other serial killers, but others who had fought their way to the top were not.
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Prof Dutton's experiment was inspired by psychologist William James who claimed that anyone who had been determined by history as successful was likely to score highly as a psychopath.
The theory was that in order to be highly successful, a person had to show the sort of charm, selfishness and ruthlessness common to psychopaths.
When ranked against the 'psychopathic spectrum', Henry VIII - who beheaded two of his wives - scored 174 against a 'starting' psychopath score of 168.
But others, like war leader Winston Churchill, romantic poet Lord Byron and top scientist Isaac Newton, scored lower.
Another of the most highly regarded figures from history, Charles Darwin, scored only 97 - lower than the average of 112 for most men.
Prof Dutton, whose book, The Wisdom Of Psychopaths - Lessons In Life From Saints, Spies And Serial Killers, will be published in paperback in the UK in September, said he was surprised by the findings.
He said: "There was only one bona fide psychopath. Henry VIII scored pretty highly for all the categories. He was top three in all of them.
"He scored very highly for emotional detachment and cold-hearted ruthlessness - both characteristics of dangerous psychopaths.
"But several of the others, while scoring highly in some of the characteristics - Byron and Oscar Wilde for example scored high for charisma and persuasion - scored lower in others.
"Byron, Wilde and Churchill may have some traits possessed by psychopaths, but they lacked others like emotional detachment and ruthlessness."
The characteristics said to be shared by all psychopaths are: Machiavellian self-interest, persuasiveness, physical fearlessness, emotional detachment, rebelliousness, feelings of alienation, carefree spontaneity, and coolness under pressure
The purpose of Prof Dutton's study is to show that many of the traits possessed by psychopaths can be beneficial and are even necessary in some fields of work.
"Psychopathy is a spectrum. Many people have some psychopathic tendencies. Just because a person is a psychopath, it doesn't make them a serial killer.
"If you take a surgeon, for example," he said. "Many have told me that if they were not capable of the sort of emotional detachment that stops them regarding a patient as someone's child or husband, then they would walk a tightrope as to whether they could do the job."
He said that while Henry VIII scored highly in many of the categories - highly enough to be a genuinely dangerous psychopath - it was possible to score higher.
Examples from history of even more dangerous psychopaths might have been figures like Hitler or Genghis Khan.
The ten figures from history assessed by Prof Dutton were: Charles Darwin, Isaac Newton, Henry VIII, Elizabeth I, Charles Dickens, Freddie Mercury, Lord Byron, William Shakespeare, Winston Churchill and Oscar Wilde.