Margaret Thatcher notoriously got by with just four hours of sleep. Now a scientific study has revealed a gene variant that may have given the "Iron Lady" her unique sleeping habits.
Researchers at the Center for Applied Genomics in Philadelphia discovered that people carrying the gene variant p.Tyr362His are able to function normally on fewer than five hours of sleep per night.
Scientists studied 100 sets of twins to find out which genetic mutations were responsible for differing sleep patterns, and found that those with the variant chose to sleep for less time than those without it.
The study, published in the journal Sleep, also found that one twin with the gene variant had 40% fewer lapses of performance during 38 hours without sleep and required less recovery sleep afterwards, resting for eight hours compared to the 9.5 hours required by his or her twin.
Dr Timothy Morgenthaler, president of the American Academy of Sleep Medicine, said: "This study emphasises that our need for sleep is a biological requirement, not a personal preference.
"Most adults need at least seven hours of quality sleep each night for optimal health, productivity and daytime alertness."
Thatcher's official biographer Charles Moore said it was impossible to know if the formidable erstwhile UK prime minister's dogged work ethic could be attributed to the gene variant.
"I do not know whether or not she had a gene of this sort," he told The Daily Telegraph. "I suppose one would know that only by conducting a genetic test.
"I think she found it hard: she wanted to show she didn't need much sleep. In fact, she needed more than she said. It was part of her desire, as the first and only woman, to beat the men.
"Though it is true that she could work very long hours and did need less sleep than most of us."
The roll call of history's most prominent figures features a number of individuals who required less sleep than usual. Benjamin Franklin claimed to need just four hours, while Napoleon Bonaparte is said to have remarked that only fools need eight hours of sleep.
Among high-profile contemporary figures, Barack Obama reportedly requires just six hours of sleep, while designer Tom Ford says he needs just three hours of rest to function properly.