In Billie Jean King's Fight for Equality, sports journalist Clare Balding talks to Billie Jean King about her influence on equality for women in sport. King put her career on the line when she accepted an offer to play against one of the world's top male tennis players, Bobby Riggs, and won. This video is excerpted from BBC’s Icons: The Greatest Person of the 20th Century, a documentary series celebrating the achievements of the most influential figures of the era.