Sir William Ivo Mallet, British diplomat, came from a Norman family, Mellet, settling in England with the 1066 Norman Invasion, was UK Ambassador Extraordinary and Plenipotentiary to Yugoslavia, 1951–1954, as well as UK Ambassador to Spain, 1954–1960, GBE, KCMG, retiring to Switzerland.
He was one of 3 sons of British diplomat, Victor Mallet, (1893–1969) and Christiana Jean Andreae.
Both, father Victor and son William Ivo, knew quite well Sir Frank Kenyon Roberts, a British diplomat who played a key role in British diplomacy in the early years of the Cold War, and in developing Anglo-German relations in the 1960s, born in Buenos Aires, Argentina.
His only daughter, Joan Elizabeth married in 1955 British diplomat Robert Alexander Farquharson, they had 3 sons and 1 daughter.