Hawthorne was born on 5 April 1929 in Coventry, Warwickshire (now West Midlands), the second of four children of Agnes Rosemary (née Rice) and Charles Barnard Hawthorne, a physician.
When Hawthorne was three years old, the family moved to Cape Town, South Africa, where his father had bought a practice. Initially they lived in Gardens and then moved to a newly built house near Camps Bay.
He attended St George's Grammar School, Cape Town, and, although the family was not Catholic, a now-defunct Christian Brothers College, where he played in the rugby team. He described his time at the latter as not being a particularly happy experience.
He enrolled at the University of Cape Town, where he met and sometimes acted in plays with Theo Aronson (later a well-known biographer), but withdrew and returned to the United Kingdom in the 1950s to pursue a career in acting.
