Four-time Olympic gold medalist Sir Mo Farah has revealed for the first time that he was trafficked to the U.K. as a young child in a forthcoming BBC documentary. “The truth is, I’m not who you think I am,” he says in The Real Mo Farah, which airs this week. The long-distance runner explains he was likely eight or nine years-old when a stranger flew him from Djibouti to London, where he was forced to take care of another family’s children. “If I wanted food in my mouth, my job was to look after those kids, shower them, cook for them, clean for them,” Farah, 39, says in the documentary, according to The Telegraph. The traffickers, whom the BBC was unable to contact, changed his name: born Hussein Abdi Karin, he became Mohamed Farah. After turning 11, the boy was allowed to begin attending school, where a physical education teacher was able to help him contact social services, and later apply for U.K. citizenship. “I felt like a lot of stuff was lifted off my shoulders, and I felt like me,” he says. “That's when Mo came out—the real Mo.”