 In 1703 he was appointed bishop of Quito (also in the Viceroyalty of Peru), where he served until his resignation in 1710 to take up the position of viceroy.He replaced Miguel Núñez de Sanabria, president of the Audiencia of Lima, who had been serving as viceroy in an interim capacity.Ladrón de Guevara had been named in the sealed instructions brought by the previous viceroy, Manuel de Oms y de Santa Pau as the successor in the event of Oms's death.