Smith was the youngest of two sons. His parents were William Smith, a mining engineer, and Elva (née Deeble) who was a teacher. The family remained in the Sinai desert until the end of
World War II, except for occasional periods of leave. In one such period, Smith was born, and lived in the Sinai desert until he was five, when he returned to the UK to live with his grandparents and aunt, Iris, in
Port Talbot where he attended primary school. It was while St Paul's School, that his interest in the subject of biology started, while on field trips. He applied to study medicine at University of Oxford. However, he discovered that he could have financial support from a Browne scholarship to study
botany at
The Queen's College, Oxford, so he changed programme. He was awarded a
Bachelor of Arts in Botany, achieving a
First-class honours in 1951. Smith immediately followed this with postgraduate research on lichens and was awarded
D.Phil in 1954. ==Career and research==