The female shark was tagged with a data transmitter off South Africa in November 2003. The unit detached automatically and was recovered off western Australia four months later. But that was not the end of the story.

Amazingly, in August 2004, five months after the transmitter bobbed to the surface off Oz, project research scientists spotted the shark - identifiable by a pattern of notches in its dorsal fin - back in its old haunt off South Africa. It had completed a round trip of some 12,500 miles in just nine months.

Only now published in the US journal Science Magazine, the research has thrown up same fascinating details about the great white's trans-oceanic abilities. The tagged shark - nick-named Nicole after the Australian film actress Nicole Kidman (isn't it nice for a great white to have a personable image for once?) - dived to a staggering 980m.

But for 61 per cent of the time, Nicole stayed within 5m of the surface. Ramon Bonfil, of New York's Wildlife Conservation Society which backed the research, told Britain's Independent newspaper: 'I'm very excited about the possibility that she was using celestial cues such as the sun or moon.

'She travelled along a very straight track; she knew where she was going � Why else would a shark go to the surface in the middle of the ocean where there are no seals, penguins or other food � unless she was trying to look at something?'

It is also thought that great whites - and other sharks - obtain a sense of direction from the Earth's magnetic field when crossing oceans.

As for a motive for such a long hike, it is thought that Nicole could have been on the hunt for a mate off Australia - thought to be a particularly active 'dating' area for the species - before swimming all the way home to give birth.

Now that's what you call commitment.

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