Serena Williams has capped off a tennis season to remember by capturing her fourth WTA Championship title.
The American great beat China's Li Na in three sets in Istanbul, triumphing 2-6 6-3 6-0 to finish off a dominant year, in which she also won the French and US Opens.
The season-ending Championship crown is the 32-year-old's 11th title of 2013 and Williams ends the year ranked world number one.
Li will reach a career-high third in the WTA rankings this week.
