CNN  — 

It was a moment in time – as brief as half a second – that captured the intensity of the relationship and rivalry between Roger Federer and Rafael Nadal.

Poised on the side of the court with her camera at the ready, photographer Ella Ling expected Federer’s farewell from tennis to be charged with emotion – though when the moment arrived, the outpouring of tears and adulation caught her by surprise.

In front of her at London’s O2 Arena were Federer and Nadal – the Swiss star’s long-time friend and rival – sat hand-in-hand while sobbing uncontrollably.

As the scene following Federer’s final match unfolded, Ling started to click away on her camera and hoped for the best.

“It was only when I got back to my computer and I downloaded everything that I found that shot and I thought: ‘Wow, that’s the one I want to share with everybody,” Ling, who follows the men’s and women’s tennis tours around the world, told CNN Sport.

The image in question – a shot of Federer’s hand on top of Nadal’s as Ellie Goulding performs “Still Falling For You” during the Laver Cup – has garnered widespread attention, capturing a scene unlike any other Ling has witnessed on a tennis court.

“I just wanted to capture an image that really summed up the feeling of the night, but also a moment in history when he [Federer] is finally playing his last match and he’s retired,” she adds.

“I would have loved to have an iconic picture, but I never imagined that I would actually get one.”

Ling's photo of Federer (left) and Nadal holding hands during the Laver Cup has proved hugely popular among tennis fans.

The Laver Cup provided an opportunity to pay tribute to Federer’s glittering tennis career, even though results didn’t go in his favor.

Playing alongside Nadal, he lost his doubles match against Americans Jack Sock and Frances Tiafoe on the first day of the tournament, then was on the sidelines for the next two days as Team Europe went down 13-8 against Team World.

But the images that will likely come to define Federer’s swansong are those of him and Nadal – rivals for more than 15 years with 42 grand slam titles between them – struggling to keep their emotions in check.

“Away from the court, I think they (Federer and Nadal) share very, very similar values and morals,” says Ling.

“They value family a lot, they value respect. They’re both very, very classy. They always win sportsmanship awards and things like that. I think that’s where they bonded.

“But at the same time, I don’t think any of us really understood quite how close they were. I didn’t realize until this moment and throughout that whole evening (when) you can just see how close they were.”

Federer (left) and Nadal watch a video montage after their doubles match at the Laver Cup.

Over the course of their rivalry, Federer and Nadal played 40 times, including in nine grand slam finals – six of which were won by Nadal. After so many battles on the court, witnessing both players reduced to tears was an arresting sight, according to Ling.

“You have these two masculine men – they’re male athletes who would … try not to show any emotion on the court, and rarely would you see much emotion off the court, either,” she says.

“For them to just be sitting there in the moment, crying uncontrollably, holding each others’ hands in front of 17,000 people there – and millions of others on TV – and just being so pure, so raw, so open about it is incredible.

“I think this will do a lot of good for society as well to see that.”

For his own part, Federer said the moment with Nadal was a “secret thank you” and that he hopes to get hold of some of the photos from the Laver Cup.

“I think all of the guys – Andy [Murray], Novak [Djokovic] and also Rafa – saw their careers flashing in front of their eyes, knowing that we all in a way have been on borrowed time for long enough already,” Federer told The New York Times.

“As you get older, you get into your 30s, you start knowing what you really appreciate in life but also from the sport.”

“You almost forgot that you’re still being taken pictures of … because obviously I couldn’t speak and the music was there, I guess I just touched him,” added Federer.

Federer waves to the crowd at the Laver Cup in London.

Ling says she was well-placed to take the photo of Federer and Nadal, out of the way of the TV cameras that shielded other photographers from capturing the shot. She hopes it can long be remembered as one of the most iconic photos in tennis – and sport more generally.

“That’s the beauty of photography,” says Ling, “You capture these moments and they’re there forever.”