Lilly King wins Olympic gold in Rio ahead of controversial Russian swimmer Yulia Efimova

Lilly King of the USA defeated controversial swimmer Yulia Efimova in the women's 100m breaststroke to claim the Olympic gold in Rio. The 24-year-old Russian was allowed to compete at the Games after she successfully appealed against a doping suspension, but was booed at she entered the aquatics centre.

Efimova was handed a 16-month ban in 2013 after traces of an anabolic steroid were found in her system. Subsequently, the International Olympic Committee ruled that any Russian athlete who had been sanctioned for doping would not be allowed to compete at the Games. However, Efimova successfully appealed her case at the Court of Arbitration for Sport.

Yet her situation was complicated further earlier this year when Efimova was given a provisional ban after testing positive for meldonium. But she has since been allowed to compete after the International Swimming Federation lifted the suspension on advice from the World Anti-Doping Agency.

The Russian, however, was not good enough to claim gold in Rio, with the most-coveted medal going to King, who won in a time of 1min 4.93secs, a new Olympic record. "It just proves that you can compete clean and still come out on top with all the work you put in," the gold medallist subsequently said, according to the BBC. "There is a way to become the best and do it the right way."

Elsewhere in the pool, Team GB's James Guy just missed out on their first-ever Olympic 200m freestyle medal after finishing fourth in the final. The 2015 world champion was only 0.26 seconds off a podium finish, while China's Sun Yang won gold in a time of 1:44.65.

However, Sun was also booed by some spectators during the medal ceremony in Rio after he served a three-month doping ban in 2014 and was jailed for driving a car without a licence in 2013.