He galloped into the stadium on his 7-year-old Australian Stock Horse "Ammo", which reared, and then Jefferys cracked his whip to signal the beginning of the Opening Ceremony.
Jefferys, who is an expert horse whisperer, also taught this difficult art to Martin Crewes (who played the title role of "The Man" in the show).
Steve Jefferys and his wife Sandra also trained their Stock Horse "Drummer" for his role of "the Colt from old Regret".
Jefferys and his Stock Horses "Ammo" and "Drummer", as well as "Jana" the Border Collie, have also taken part in other equestrian events, including "Equitana 2002" in Brisbane, Queensland.
Steve Jefferys appeared, with his horse "Ammo", on "Weekend Today" on the Nine Network in Australia on Saturday, 9 September 2010, celebrating ten years since the 2000 Summer Olympics in Sydney.