LONDON (Reuters) - A lot has changed since tennis turned professional in 1968, from the colour of the balls to players’ hairstyles and advances in racket and string technology.
But one thing remains the same; winning the French Open and Wimbledon in the same year is still arguably the sport's biggest challenge.
Since Rod Laver did it in 1969, only three men – Bjorn Borg, Rafael Nadal and Roger Federer – and six women - Margaret Court, Billie Jean King, Chris Evert, Martina Navratilova, Steffi Graf and Serena Williams – have managed the feat.
The change in surface from clay to grass, and the fact that the two events are almost back to back in the calendar, have always made it a tough proposition.
"It’s easily the toughest challenge in tennis," said Mats Wilander, who won the French Open three times but never made it past the quarter-finals at Wimbledon.
"I think more in men’s professional tennis than in women’s, because it’s harder to break serve. I think it’s by far the toughest challenge we have in men’s professional tennis."
When Wimbledon decided to move back a week in the calendar, in 2015, it was intended to extend the grasscourt season and give those who had been involved in the latter stages in Paris more time to adapt.
Serena Williams certainly took advantage when she did the double in 2015, but on the men’s side no one has managed it since Nadal did it for a second time in 2010.
Wilander, who will be working as a pundit for Eurosport during Wimbledon, said the extra week between the two grand slams helped, noting that the change in style of play was even tougher in his day as the grass at Wimbledon was much faster then.
"The difference between clay-court tennis and grass-court tennis in those days, it’s not even comparable. I would serve and volley on both serves because otherwise you would be laughed at by all the Australians.
"It was difficult to make the right choice at the right time. It didn’t come naturally when you have such little time to prepare for a new surface and it’s not your natural way of playing."
World number one Andy Murray won his second Wimbledon title last summer, when he also reached the final at Roland Garros, and said the extra time was invaluable.
"It makes a huge difference. Just a bit more time to adapt to the courts and let your body get used to playing on grass again," he said last week.
"(Before), literally, sometimes it was like one or two days. I mean, it was ridiculous, looking back at it, really."
Between 2008 and 2010 it seemed like the difficulty was overstated, as Nadal (twice) and Federer (in 2009) did the double.
But all nine players to do it have won at least 10 grand slam titles, so perhaps it's more that only the greatest of all can achieve the feat.
When Nadal won Wimbledon in 2010, he said winning either slam was not so difficult in itself, but that the effort spent in winning in Paris meant it was easy to run out of steam.
"You are coming from American hard-court season," he said at the time. "So one month in America, then two months in Europe, playing on clay. Then mentally if you are able to win Roland Garros, you already played a lot of time at your top, mentally and physically."
Nadal and Jelena Ostapenko, who unexpectedly won her first grand slam title this month at Roland Garros, will try to do it again at Wimbledon.
The Latvian won the junior title at the All England Club in 2014 but Nadal has not been past the fourth round since he reached the final in 2011.
"I played five finals in Wimbledon (but) since I have had problems with my knee, since 2012, playing on grass has been very complicated for me," said Nadal, who pulled out of last week’s Aegon Championships at Queen’s Club soon after he won his 10th French Open title.
"We'll see how my knee behaves. Playing on grass is very special. You need to play at a lower level. The body posture is down. You have less stability. On grass, anything can happen."
editing by John Stonestreet