When Billie Jean King won the 1972 US Open, her prize money was $10,000. The men’s champion – Ilie Nastase – took home $25,000.
The following year, King formed the Women’s Tennis Association (WTA), with a mission to achieve equal pay.
Later in 1973 came an unlikely episode in that campaign – a bizarre, one-off match known as ‘The Battle of The Sexes’ in which King, 29, took on 55-year-old former men’s world number one (and self-proclaimed male chauvinist) Bobby Riggs.
Austin told BBC Sport it “wasn’t just a tennis match, it became an event around the world”.
In the build-up to the televised match, Riggs made it plain he felt women were inferior to men. King saw him off in straight sets.
Briton Sue Barker, who would later win the French Open, recalls how important it felt. She remembers her coach calling to say: “Your hobby has just become a career.”
Later that year, the US Open introduced equal pay for male and female players. The Australian Open began offering equal prize money in 1984, but reversed that decision in 1996, then again in 2001. The French Open and Wimbledon introduced parity in 2007.