Here's the woman, the eyes of the world are on, 25-year-old Castus Semenia of South Africa,

the 2009 World Champion, Silver in London four years ago.

Can she go one better in Rio?

Off they go.

Semenia making a statement of intent in the first few metres.

Castus Semenia has a condition known as hyper and geoginism, which means that she has excessive levels of male hormones.

She looks very, very comfortable as she has gone all season.

The South African government has brought in scientists and physicians to argue Semenia should not be required to lower her natural level of testosterone.

And this could be Semenia's day.

The battle between Castus Semenia and the IWAF has reached a crucial stage.

She's normally got a devastating kick when she goes and goes she does.

She's left the others in her wake and Castus Semenia is going to do what most people thought she would do in the 800 and she runs away and wins it brilliantly.

It isn't every day that the whole world is up in arms about track and field, but yesterday we got one of those days

and today and probably even tomorrow because right now there's a track and field story that's about so much more than winning a race.

This married the ethics of sport, the eligibility of what it is to take part in sports and also what it means to be a woman.

Megamohan has been reporting on a South African runner named Castus Semenia for the BBC.

Castus Semenia was born in a very rural community on the edges of South Africa.

She was born a woman and she was raised a woman. She doesn't come from money. She calls herself a bush girl.

You know, always in the bushes to be honest, I grow up more with boys so I never like to play around girls because I always thought girls were too soft.

And she was really, really good at athletics.

They always treated me more like, okay, this one is crazy so let her do what she likes.

We spoke to her coach who she calls her dad yesterday and he said that he knew that she had this prowess, this gift for running from a very, very young age.

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