Hurst was born in Nelson, New Zealand in 1915, the son of Percy Cecil Hurst, a commercial traveller, and his wife Margery Whitmore.  He attended Nelson College from 1927 to 1932, and then was a student at Canterbury University College in Christchurch, from where he graduated with a Master of Science degree in physical chemistry in 1939. While at Canterbury, Hurst was a member of a student group assisting European Jews to escape the Nazis.
Following his graduation, Hurst was en route to the United Kingdom by ship to undertake doctoral studies at Emmanuel College, Cambridge, working his passage as a radio operator, when World War II broke out.