Caster Semenya was just 18-years-old when she won gold in the 800 metres at the 2009 World Championships in Berlin.

Her victory was controversial because the South African runner was facing questions over her gender. So much so, that she was made to take a gender test on the eve of the final.

The test revealed that the teenager had been born with internal testes and no womb. It meant she had higher levels of testosterone; a hormone that increases muscle mass and strength.

She has been speaking to Matt Pintus after the launch of her memoir, The Race to Be Myself.

(Photo: Caster Semenya at the 2009 World Championships in Berlin. Credit: Getty Images)