The former world 800 metres champion Caster Semenya qualified for the London Olympics when she eased to victory at a local meet in Pretoria.
The South African underwent gender tests at the 2009 Berlin world championships where she won the 800 gold medal.
The 21-year-old did not compete for almost a year until the International Association of Athletics Federations cleared her to run again after accepting the conclusions of an expert medical panel.
Her time also made her the first woman in 21 years to run under two minutes on South African soil.
