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English academic and professor of Leadership Studies at the University of Surrey, John Adair posed in front of a Venn diagram at the University in Guildford on 18th December 1979. (Photo by United News/Popperfoto/Getty Images)

English academic and professor of Leadership Studies at the University of Surrey, John Adair posed in front of a Venn diagram at the University in Guildford on 18th December 1979. (Photo by United News/Popperfoto/Getty Images)