Murray is turning up the heat in Australia

For Murray, it meant coming through a two-hour exhibition match in the Kooyong Classic against Croat No 1 Ivan Ljubicic.

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In the case of Yorkshire's O'Brien, she was the last woman standing in her first-round match in qualifying, which she was awarded when her opponent Darya Kustova could no longer carry on.

There was no starker warning of the dangers of the heat at the year's first Grand Slam than the sight of the tournament medical staff tending to the horizontal Belarusian.

Trailing 6-3, 1-0, Kustova failed to emerge from the changeover and O'Brien, ranked a humble best-of-British 127 in the world, was handed the match before her opponent was helped back to the locker rooms.

Murray's match was no more than glorified practice at an event that guarantees its participants three round-robin matches in the build-up to the Australian Open next week, but the way he went about winning 6-7, 6-4, 6-2 was instructive.

Murray can assert he is entering this Grand Slam with mind and body in better shape than ever. Against Ljubicic, he trailed 6-7, 0-3, having missed two sets points in losing the tiebreaker 9-7.

Given the heat, the match's lack of ranking significance and his residual jetlag, there would have been every excuse just to let it go.

But as he began to attack the net both to shorten the points and practise his volleying, the winning habit kicked in. He reeled off five consecutive games, defying temperatures well over 100F and a gusting, hot wind.

'I'm feeling really good. I trained hard in the off-season and I've been preparing pretty much solidly for this for seven weeks now,' said Murray, who has added yoga to his new training regime. 'Regardless of how well you train it's important to win matches and I did that at Doha last week.

'I don't mind the heat. When it's hot other guys tend to get tired and make more mistakes when I mix it up.'

Murray, who was seeded ninth in today's draw, has been getting used to the fluorescent blue Plexipave courts that will be used for the first time this year and Wilson balls that some players have complained are too slow and heavy.

The Australian court, coloured to aid the sighting of the ball on television, plays similarly to the surface at the U.S. Open, but Murray believes it scuffs up the balls as they get older, making them feel 'bigger'.

The advantage of the new surface compared to the Rebound Ace it has replaced is a supposedly more-even bounce and the fact that it does not get sticky when hot.

There have been six British players in qualifying, two men and four women. Alex Bogdanovic, O'Brien, Elena Baltacha and Anne Keothavong made it over the first hurdle while Jamie Baker is through to the third and final round tomorrow.