Competitiveness, like all things, is a practice. But I was born with it baked in, a head start, a small beast locked in a too-small cage, snarling at the bars whenever there was a task at hand. My mother started feeding it young. Maybe she'd learnt what my father had always known: that I might have to work twice as hard to have half as much.

Rebecca was born a ?freedom baby', a child whose birth coincided with the fall of the apartheid regime in South Africa, to a white mother and Black father. She was in-between, a breathing blend of her parents' skin, well-acquainted with that unsettling sense of non-belonging from an early age. But the water welcomed her strong body and she caught the eye of coaches at swimming schools in the UK. Fuelled by a natural competitiveness honed on the sharp edge of her mother's love, Rebecca plunged into the hothouse of British swimming, and soon was persuaded to swap sporting nationalities, leaving Kenya behind to pledge allegiance to Great Britain.

Rebecca learns that training is designed to be punishing - to break down, excoriate, and puncture pain barriers. She learns that to swim a perfect race is to experience a sort of ecstatic communion between body and liquid world. And she also learns that her body, her Black body, is a commodity that other people feel entitled to, whose performance is constantly scrutinised, debated, and subjected to a racism both universal and endemic to the white world of swimming.