Celebrated sex expert Victoria Johnson has died, aged 88. One half of the pioneering husband and wife research team Masters and Johnson, her sex studies in the 1960s led to two bestselling books. Johnson grew up in rural Missouri and was a twice-divorced single mother when she became an assistant to obstetrician-gynaecologist William Masters at Washington University in St. Louis in the late 1950s. The pair became lovers and co-collaborators in a series of sexual experiments. Their books Human Sexual Response and Human Sexual Inadequacy were both bestsellers. She died in St. Louis on Wednesday (24Jul13).