Vera Caslavska, one of the most decorated gymnasts, has died aged 74 after battling pancreatic cancer.
A vocal critic of the Soviet Union, Caslavska was forced into hiding in 1968 after signing a document calling for political reforms.The Two Thousand Words manifesto advocated change in Czechoslovakia but angered leaders in the neighbouring Soviet Union which invaded the country two months later.
Caslavska fled to a mountain village but was later given permission to return to the Olympic team, which she did just weeks before the Mexico Olympics in the same year.
She went on to win gold in the vault, the individual all-round, the floor exercises and the uneven bars, before turning her head in silent protest during the Soviet Union national anthem.
After retiring from gymnastics, Caslavska served as president of the Czech Olympic Committee (COC), won the Pierre de Coubertin Prize for promoting fair play in 1989 and was also awarded the Olympic Order.
Her achievements in winning four golds at Mexico put her in exalted company, alongside Biles, Agnes Keleti and Larisa Latynina for Hungary and the Soviet Union respectively in 1956 and Romania's Ekaterina Szabo in 1984.
Jiri Kejval, president of the COC, said that Caslavska was "a fighter" and that she "died in her sleep".