Nguugi wa Thiongo'o is a Kenyan author who spent some twenty-two years in exile because of threats to his life for his beliefs in Fanonist Marxism under the dictatorship of Arap Moi.
But before his return to his home country, Thiongo'o did write in English. His first novel, Weep Not, Child was written while the author and activist attended the University of Leeds in London, England. His second work, The River Between, was also written in English. His third novel, A Grain of Wheat, in 1967 is the work in which Thiongo'o embraces Fanonist Marxism. After its publication, Thiongo'o changed his name from James Ngugi, renounced both English and Christianity, and began composing in his native language, Gikuyu, as well as Swahili.
Eventually, Thiongo'o returned to writing in English as well. Random House published is novel The Wizard and the Crow in 2006, which Thiongo'o translated from Gikuyu to English. Thiongo'o is currently Distinguished Professor of English and Comparative Literature at the University of California-Irvine after a long tenure at NYU.
He stopped writing in English because he renounced the language in order to promote his native language, Gikuyu. This is stated above.