Mahathir Mohamad was sworn in as Malaysia’s seventh prime minister on Thursday following his stunning election victory over the coalition that has ruled the Southeast Asian nation for six decades since independence from Britain. Malaysia’s constitutional monarch, Sultan Muhammad V, administered the oath of office, in a ceremony carried live on state television from the palace. Mahathir, 92, has become the oldest elected leader in the world, Reuters reports. Mahathir ruled Malaysia with an iron fist from 1981 to 2003, and came out of retirement to take on his former protege, Najib Razak, who was prime minister for nearly a decade. Mahathir’s alliance of four parties trounced Najib’s Barisan Nasional, the first time it had ever lost an election.