Nigeria's Ngozi Okonjo-Iweala was appointed as director-general of the World Trade Organization (WTO) on Monday. She is the first woman and first African to take on the role. She has been Nigeria's finance minister and also briefly served as foreign minister. She has had a 25-year career at the World Bank and was chair at Gavi, the Vaccine Alliance. "This is groundbreaking and positive," she said.