It is almost exactly 40 years since two young Australians had what has become a famous encounter with a lion in the depths of the African bush.

John Rendall and Anthony Bourke had come across "Christian" late in 1969, at what was then a zoo in the upmarket London department store, Harrods.

Alan Johnston speaks to John Rendall about their decision to release him into the wild in Kenya and the extraordinary moment that became a YouTube sensation.