
Billie Jean King has been a pioneer in the fight for equal rights in sport since starting her professional tennis career in 1959. She was rewarded for her tireless campaigning by President Barack Obama, who awarded her the Presidential Medal of Freedom in the East Room of the White House in 2009.

King (then Moffitt) plays a forehand volley during her Wimbledon semifinal in 1964. She would win her first major title at the All England Tennis Club in 1966.

King won half of her 12 career majors at Wimbledon, between 1966 and 1975. She was also instrumental in the formation of the Women's Tennis Association in 1973 that battled for equality in the sport.

in 1973, King agreed to play former world number one Bobby Riggs in a clash that was dubbed the "Battle of the Sexes." With $100,000 up for grabs for the winner, a television audience of millions tuned in.

Riggs, then retired and aged 55, had made a fortune gambling on his own matches during his career, and had beaten Margaret Court before playing King. He lost in straight sets.

Riggs and King embrace after the match at Houston in 1973. King said had she not won she would have "set us back 50 years."

King says there is still some way to go to alter attitudes in tennis. She told CNN a New York Times article on the body shape of world No.1 Serena Williams this year drove her crazy: "So what? stop evaluating us. I mean, she is probably the all-time great. So stop it. Talk about her accomplishments."

King, along with ex-husband Larry, set up World Team Tennis, a professional league with a team format, in 1973. Here she is joined by a cast of players present and past at a charity day -- including Lindsay Davenport, Andy Roddick, Serena Williams, Anna Kournikova, Tommy Haas and Jan-Michael Gambill -- as well as pop star Elton John.

King, in her role as captain of the United States Fed Cup team, gives a pep talk to Monica Seles during a 2000 tie against Belgium. She led the U.S. to four titles during her reign and was handed the Fed Cup Award of Excellence in 2010.

WTA founder King is flanked by Maria Sharapova and Serena Williams at a special gathering of former world No.1s to mark the 40th anniversary of the organization.