Melinda, wife of the Microsoft founder and co-chair of their multibillion-dollar charity foundation, told Time magazine she and Bill sometimes fantasise about their dream location.

" 'When Bill and I play that game where u can live anywhere,' Melinda Gates just told me, they'd choose...Sydney," Time editor-at-large Belinda Luscombe tweeted on Tuesday.

One sceptic on Twitter wondered whether "they say that to all the Aussies"; Luscombe was born in Sydney and attended the University of Sydney.

But the Gates have had ample chance to enjoy the spoils of the Emerald City. In 2011, they holidayed for a month with their children in a three-storey Vaucluse mansion that cost $25,000 a week.

Manly Pavilion proprietor John Codling remembers them leaving "a generous tip".

"When Bill and I play that game where u can live anywhere," Melinda Gates just told me, they'd choose... Sydney. Full i/view in next @TIME — Belinda Luscombe (@luscombeland) November 17, 2014