At the 1960 Summer Olympics in Rome, on 27 August 1960, at the age of 19, she won gold in the 200 m breaststroke in 2:49.5 ahead of West Germany's Wiltrud Urselmann (2:50.0), setting a new world record time. She was one of only two GB gold medallists that year, the other being Don Thompson in the 50 kilometre walk.
She is married to cycling commentator and former leading British professional track cyclist Hugh Porter; they met travelling to Tokyo for the 1964 Summer Olympics and married in 1965. The couple live in Wolverhampton, and, after a spell teaching swimming including the P.E. Dept at Ounsdale High School, she is currently a sports commentator and journalist for The Daily Telegraph, under the name Anita Lonsbrough-Porter.