In the immediate aftermath, Riggs said he had underestimated King. “Whenever I thought I had the point won on our exchanges, she saved it,” he said.

Later, there were allegations that Riggs had deliberately thrown the match, external to pay off his gambling debts to the Mafia.

Whatever the circumstances, King’s victory has stuck in the public mind. Not a day goes by when someone does not mention the Battle of the Sexes to her.

“When I met President Obama in the Oval Office for the first time, he said ‘I watched that match when I was 12. I have two daughters now and it made a difference in how I raise them’,” King said.

“The women who saw it, it empowered them and gave them self-confidence.

“And the men come up to me and they’re the ones who are very emotional – sometimes they have tears in their eyes.”

King and Riggs, who died in October 1995, stayed in touch afterwards, and he remained a sporting hero to her.

“We stayed in touch and the night before he died, I had a great discussion with him,” King said.

“He finally understood it was about history. I used to say to him it was about history, and he said no, it was about money.

“He told me he loved me and the next day, he passed away.”

King ended her career with 39 Grand Slam titles across singles, doubles and mixed doubles.

But she is remembered just as much for her fight for equality in sport, and beating Riggs was a crucial part of that.