Irwin, 44, who was killed on Monday by a stingray while filming an undersea documentary, had bought the land,about the size of the Isle of Wight, to preserve the habitat of koalas and porcupine-like echidnas threatened by land clearance.

He had repeatedly urged individuals as well as corporations to buy and preserve the habitats of threatened species. “You know, easily the greatest threat to the wildlife globally is the destruction and annihilation of habitat. So I’ve gone, ‘Right, well, how do I fix that?’ Well, making a quid here. People are keen to give me money over there. I’ll buy it. I’ll buy habitat,” he said in an interview. Most of the land is in Queensland.

After viewing footage of his final moments, Queensland police said yesterday that Irwin had not been intimidating the fish that killed him.

The naturalist died after being stabbed in the heart by the barbed tail of a bull stingray, thought to weigh about 220lb (100kg), during filming on the Great Barrier Reef. The footage shows Irwin swimming above the ray when it lashes out with its tail, a movement performed when stingrays feel threatened. Irwin then pulls the serrated barb from his chest.

“He pulled it out and the next minute he’s gone,” John Stainton, Irwin’s manager and friend, said. “The cameraman had to shut down. It’s a very hard thing to watch because you’re actually witnessing somebody die . . . it’s terrible.”

Although the barb, which can measure up to 8in (20cm), delivers powerful venom, scientists said that the trauma inflicted by the serrated bone had probably killed Irwin.

John Howard, the Prime Minister, interrupted Parliament yesterday to pay tribute to Irwin. He said that his death had shocked and horrified people and “brought forth an outpouring of grief and an outpouring of emotional expressions of regard for this remarkable man around the world”.

Hundreds of fans placed flowers and tributes, including messages on khaki shirts similar to those Irwin wore, outside his Australia Zoo in Queensland. His family has been given the option of a state funeral.

In Thailand 20 elephant keepers put up a poster of Irwin and laid a wreath before holding a minute’s silence and a reading of a tribute at the Ayutthaya Elephant Palace, 50 miles north of Bangkok. Irwin is said to have promised a donation of a million baht (£14,000) to an elephant project.

Princess Rangsinopdol Yugala said: “Steve lived life as if on the wing of the dragon. His spirit matched our ancient Thai warriors who fearlessly rode the great musth elephants into battles.”

Discovery Networks, which owns the cable TV channel that screens Irwin’s documentaries, said that it had not decided whether to screen the footage of his death.

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