Colonization, as a means of reforming Ireland, had been advocated by certain Anglo-Irish politicians and English administrators since the early sixteenth century. This policy had been activated in 1548. Sir Thomas Smith (1513–77), a leading political and intellectual figure, contributed to the policy's development in the early 1570s with his colonial venture in eastern Ulster. Under Elizabeth, he served as ambassador to France on two occasions and held the principal secretaryship between 1572 and 1576. Smith is regarded as an important English humanist. His main works, A discourse of the commonweal of this realm of England (1549) and De republica Anglorum (1565) analyse respectively the economic problems and the legal and political system of the period.