She has the royal touch, or topspin! Catherine, the Princess of Wales got tennis legend Roger Federer to pop out of retirement for a special occasion on the famous grass courts of Wimbledon.

Kate Middleton and Federer were joined by the ball boys and girls of Wimbledon ahead of the Grand Slam tournament that begins next week.

Middleton took to ball girl duties while Federer served at the baseline, learning how to feed the ball to the Swiss athlete. When the ball was returned, Middleton caught it without letting it bounce. 

Although Middleton was praised for her "good catch," Federer quickly reminded everyone why he was the all-time male champion of the tournament with eight singles titles. "Are you allowed to do that?" he cheekily asked ball girl Mollie of Middleton's no-bounce catch.

Kate Middleton in a white top and skirt holds a tennis racket split Roger Federer on the baseline in white looking back at the Princess of Wales

Kate Middleton made a small Ball Girl error while practicing with the Ball Boys and Girls of Wimbledon and Roger Federer. (Wimbledon/YouTube)

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"Oh yeah, are you allowed to do that?" the Princess inquired.

"In Australia they would catch it, but in Wimbledon they don't," Federer said, noting the difference between the Australian Open and Wimbledon.

"Ah, OK," Middleton said, as Mollie explained that part of their responsibility as ball girls and boys was to allow the ball to bounce before retrieving it.

Kate Middleton holds a ball up in the air as if she were to feed it to the player on the baseline next to another young girl

Kate Middleton properly demonstrated how to feed the ball to a player. (Handout/Thomas Lovelock - AELTC)

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When the two switched roles, Middleton joked with Federer, "Any tips on my serve at the same time would be very helpful."

"The serve looks great," the 20-time Grand Slam champion replied.

The two also played a bit of mixed doubles – on opposing teams. Middleton and Federer rallied, before Middleton hit a point-winner that struck the line.

"I think it was on the line," Federer laughed, slightly shocked. "Amazing."

Kate Middleton with her hands on her hips in white talks with Roger Federer on the court of Wimbledon

Kate Middleton stole a point from Roger Federer and his mixed-doubles partner, much to the champion's delight. (Handvout/Thomas Lovelock - AELTC)

Donning their Wimbledon white, Middleton and Federer were also given a challenge on the grass courts – to execute the ball change – which includes rolling the tennis ball down the court from one person to another in a straight line. 

They also practiced inside on hard courts with the boys and girls who would be working the tournament.

Kate Middleton and Roger Federer both make lunging motions as they toss tennis balls for Wimbledon

Kate Middleton and Roger Federer practiced the routine of a ball girl and boy at Wimbledon, ahead of the Grand Slam tournament's start next week. (Handout/Thomas Lovelock - AELTC)

"With the discipline and everything that you've learned from here, you'll be able to take it in to so many other different parts of your life. Things like confidence. And as you're saying… that feeling of pride being on any of the courts, actually, is such a big moment. So, it's [a] good choice," Middleton told a lucky few ball boys and girls.

"To see the training and the dedication and the amount of time that's put into training and making sure this sort of goes well on the day, for the champions who are playing at Wimbledon," Middleton later motioned to Federer, among a larger group of kids, "It's incredible to see it behind the scenes, so thank you. I've really enjoyed it."

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Wimbledon begins July 3 in London.