[1] Haythorne was born in Adelaide, South Australia, the child of an English father and an Australian mother of Irish descent.
With Harold Raymond, he took part in comedy sketches, played his piano accordion, sang songs, and danced.
With that company, he mounted works by a number of Australian choreographers, including Graeme Murphy, Garth Welch, Don Asker, Rex Reid, Leslie White, and Ray Cook, and he introduced the ballets of choreographers he had worked with in the United Kingdom, including Walter Gore, Jack Carter, and Peter Darrell.
He also engaged the Danish dancer and teacher Hans Brenaa to stage La Sylphide and other works of August Bournonville.
[9] He remained in this role for another three years, but, after deciding that he wanted to direct a company rather than head a dance school, he accepted the position of artistic director of the Royal New Zealand Ballet in 1981.
[11] For the company's sixtieth anniversary in 2013, encapsulating his attitude to his appointment in 1981, and also his approach to directorship in general, he wrote: "I knew I had to learn much more about New Zealand and its history, familiarise myself not only with its dance world but also with its literature, music, and visual arts, while still keeping a finger on the international pulse.
[14] In the 1993 New Zealand New Year Honours, Haythorne was appointed a Member of the Order of the British Empire, for services to ballet.
He returned to the stage himself on several occasions with productions by the Australian Ballet, taking cameo roles in Stanton Welch's Cinderella (1997), Graeme Murphy's Swan Lake (2002) and Nutcracker: The Story of Clara (1992, revived 2003), Ronald Hynd's Merry Widow (1975, later revived), and the joint Australian Ballet–Sydney Dance Company production of Murphy's Tivoli (2001).
When his will was read, it was learned that he had requested a party celebrating his life rather than a somber memorial service with a eulogy.
Accordingly, on 31 January 2015, simultaneous celebrations, linked by video, were held in the studios of the Australian Ballet in Melbourne and the Royal New Zealand Ballet in Wellington, Many members of the dance and theatre communities in both countries attended and shared affectionate anecdotes and stories.