In 1970 he married Streatham's Cathy McGowan of Ready Steady Go fame at St Barthlomew's
Bennett was born in Garnant, Carmarthenshire, son of Gorden, a police officer, and Sarah Gwen (nee Lewis).
His brother, Alun became an actor under the name Alun Lewis. At the age of 15, while attending Henry Thornton grammar school, Clapham, Bennett joined the National Youth Theatre.
He played the female role of Ophelia in Hamlet (Queen’s theatre, 1959) when it became the first amateur company to perform in Shaftesbury Avenue and was still casting only male actors, as in Shakespeare’s time – a practice that changed shortly afterwards. He continued with the company for five years, his roles including Richmond in Richard III (Scala theatre, 1963).