Unchallenged by the plethora of extra big-money events being crammed into the tennis calendar, the sport's four Grand Slams remain its absolute pinnacle and those in which the greatness of its stars are judged.

Melbourne, Roland Garros, Wimbledon and Flushing Meadows provide tasks so daunting and different that only two men and five women have claimed the clean sweep of singles crowns in the Open era.

Today such an achievement is tougher than ever, with the days when three of the four majors used to be played on grass long gone and the gruelling jolt from the thick clay of France to the Wimbledon lawns as pronounced as ever.

The Slams have risen above recent controversies over changes in the tennis calendar, with the growing financial clout of the ATP's Champions Series and the WTA's Premier tournaments failing to impinge on their importance.

The most recent suggestion, that the gap between the French Open and Wimbledon be extended to three weeks to allow players to adapt to the shift in surface, was roundly rubbished by the performance of Rafael Nadal in 2008.

With prize-money parity now established across the board and a Centre Court roof complete to minimise the risk of complete wash-outs at Wimbledon, the Grand Slam tournaments are continuing to adapt to meet the demands of the modern game.

With rivalries like Nadal and Roger Federer breaking new ground, as well as the continued emergence of Russian challenges to the Williams sisters' reign in the women's game, their good health seems assured for some time to come.