Discussion of natural genius irritated him; he insisted that immense hard work separated first rank mathematicians from many of those who fell short. Recent accolades, from the 2003 Karp prize to last year's Tarski lectures underlined that commitment. Widely regarded by colleagues as among the best mathematical logicians under the age of 50 in the world, he would have been a potential contender for any of the great mathematical prizes on offer. Yet his modesty was total. The only time he got excited about an award was when a fellow Australian won the Fields medal, the maths Nobel.
Hard work was also an approach he had taken to chess, something that had been a passion since he first became interested at the age of six, when he and his parents, Robert, a neurologist, and Noela, an artist, were living in London. Once he'd learnt the basics, his father remembers, ''there was no stopping him''.
UPDATE: The UCLA's Mathematics department also has a tribute to Greg Hjorth including a PDF file that contains pictures of the man while in action, both inside the classroom and over-the-board.