Andre Agassi kisses his wife and partner Steffi Graf during their mixed doubles match against Tim Henman and Kim Clijsters at an exhibition event to unveil the new retractable roof over Centre Court at Wimbledon in London, on Sunday.

Agassi, Graf, Henman and Clijsters rolled back the years as they featured in mixed doubles and singles matches under the new roof. Incidentally, it was raining, but the roof ensured there was no stoppage in play for the first time at Wimbledon due to rain.

Henman and Clijsters won the opening mixed doubles, played for just one set 7-6 (7-5).

Clijsters is making her competitive comeback in August during the US hardcourt season. The Belgian had turned her back on tennis two years ago aged 23 but after getting an invite to play in Sunday's exhibition event, she discovered she wanted to test her skills on the WTA Tour again.

Graf reacts after Agassi accidentally hit a ball straight at Clijsters.

The roof will be operational for the first time when the tournament begins in June, guaranteeing play on the showcourt whatever weather is provided by the fickle English summer.

While the roof allows sufficient light for play in most conditions, a system of 120 lights means play can continue in fading light and when it is dark outside.

Clijsters serves during her singles match against Graf, which she won 6-4.

Getting body and mind on the same wavelength was the biggest challenge Clijsters faced as she prepared to step back under the spotlight at Wimbledon.

"My first few weeks were mainly getting the basic exercise, getting everything into place after having a baby, because a lot changes, your body changes. That was in my mind," she said.