Paul McCartney has revealed a source of inspiration behind The Beatles’ song Lady Madonna. McCartney told National Geographic’s editor-in-chief Susan Goldberg that the 1968 hit was partly inspired by a photograph of a Malayo-Polynesian woman surrounded by three small children. It was taken by photographer Howard Sochurek, and appeared in an article titled American Special Forces in Action in Viet Nam, in National Geographic’s January 1965 issue.One particular issue I saw in the Sixties had a woman, and she looked very proud and she had a baby. And I saw that as a kind of Madonna thing, mother and child, and I just… You know, sometimes you see pictures of mothers and you go, ‘She’s a good mother.’ You could just tell there’s a bond and it just affected me, that photo. And so I was inspired to write Lady Madonna, my song, from that photo.Photo: Howard SochurekThe revelation was part of an interview in which McCartney promoted Meat Free Monday’s new campaign One Day A Week. A documentary of the same name has been launched to highlight the environmental impact of animal agriculture. It features Paul, Mary and Stella McCartney, plus actors Woody Harrelson and Emma Stone.The film includes tracks from McCartney’s 1997 classical music album Standing Stone, plus an unreleased song titled Botswana.