Mark St Leon is a circus historian whose forebears established one of the first travelling circuses in Australia in the 1850s and remained active in circus both in Australia and the USA until the 1960s. St Leon spent three years of his boyhood in San Francisco, California, where his father, an airline pilot, was based. He later returned to Australia and attended Sydney Grammar School 1962-69. Following this he graduated with a Bachelor of Economics from the University of Sydney.