British thesp Joseph Mawle (“Game of Thrones”) has joined Thandie Newton, Chiwetel Ejiofor, Anika Noni Rose and John Boyega in “Half of a Yellow Sun,” with shooting under way in Calabar, Nigeria.Film is based on Chimamanda Ngozi Adichie’s novel about the struggle to establish the independent republic of Biafra in Nigeria. Andrea Calderwood and Gail Egan are producing the feature debut of Nigerian theater director, playwright and novelist Biyi Bandele, who is helming from his own adaptation. Exec producers are Yewande Sadiku and Muhtar Bakare. The cast also includes Nigerians Onyeka Onwenu, Genevieve Nnaji and Zack Orji. Newton and Rose portray twin sisters while Ejiofor plays a professor and Mawle an English writer. Filming will continue until June 23 on location in Nigeria and in London. International sales are handled by Ealing Metro.