As he did pretty much everywhere he went, Federer did a lot of winning at the ATP Finals over the years.
Specifically, he won 59 matches over a span of 17 years, and plenty of those wins were hugely significant ones, leading him to six titles.
Just as significant as any of those though, despite only being a group stage match, was his final victory at the tournament.
Why? Because it was the last time that the world got to see Roger Federer at his glorious best.
It was the winter of 2019, and Federer was heading into the Finals on the back of a second half of the year that had been full of heartbreak.
He had lost the Wimbledon final to Novak Djokovic after failing to take two match points on his own serve and then lost to Grigor Dimitrov in the US Open quarter-finals after being two sets to one up, looking like a player in the final stages of his career for perhaps the first time as he struggled with the humidity and back pain.
He had bounced back by winning the 100th title of his career on home turf in Basel, but expectations were low heading into the year-end event nonetheless, especially as he was drawn in a group with Djokovic and Dominic Thiem, two of only three players on the tour that he had a losing head-to-head record against.
Those who were pessimistic about his chances in London were proven right when he lost his opening match in straight sets to Thiem, and even after a victory over Matteo Berrettini in his second, a group-stage exit still looked likely given he'd have to beat Djokovic to avoid such a fate.
He hadn't done so since 2015, and the Serb wouldn't be taking it easy either given that, after losing to Thiem too, he also had to win to progress to the semi-finals.
Fans of Federer feared that, after the narrow defeat in the same city four months prior, this would be the match that would confirm once and for all that their man was no longer at the same level as his great rival.
However, for one last time, the 20-time Grand Slam champion had other ideas.
It was immediately clear that he meant business, with the Swiss player attacking Djokovic from the off to get a break point in the opening game before holding his own serve with two inch-perfect aces.
He then gained a break point again in the third game with a sumptuous backhand and this time made it count, producing another after playing a perfect forehand slice to win a tough rally and take charge of the contest.
Making the most of the fast surface, Federer remained on the front foot and looked far more likely to break serve again than have his broken as he moved closer and closer to going a set up.
That's because he was serving as well as he ever had, hitting just four faults, not facing a single break point and losing just three points in his service games against the best returner of all time.
He was more than holding his own when the ball did make its way back across the net too, hitting 12 winners to Djokovic's seven and making just two unforced errors to Djokovic's six in a first set that ultimately only lasted 38 minutes.
As he returned to his seat at the end of it, thousands of adoring fans throughout the O2 Arena couldn't contain their excitement at seeing their hero roll back the years and brush away all their fears that his time at the top was over.
However, their fears about him losing the match would have very much remained. After all, this was an all-too-familiar scenario.
So many times before in their rivalry Federer had played beautifully in front of a crowd cheering his every move and Djokovic's every mistake, only for the Serb to spoil the party.
Especially with what happened on the other side of the city months earlier, it was hard to shake the feeling that once again - to paraphrase A Game of Thrones - Federer would play valiantly, Federer would play nobly, Federer would play honourably. And Federer would lose.
It did indeed look as if history would repeat itself when the Swiss player failed to convert a break point in the first game of the second set and then faced his first break point of the night three games later, but even history was no match for Federer's tennis that evening.
He stopped Djokovic from taking a 3-1 lead by following up a ferocious forehand down the line with the coolest of volleys and then served his way out of trouble with ease.
In the very next game, a few errors from the Serb that seemed unavoidable gave him three break points, and he took the second of them to move a step closer to what would be a hugely cathartic victory.
Federer never looked like choking as he had at Wimbledon after that, losing just two points in his next two service games before breaking Djokovic to love to claim victory.
Over the years, he mastered the art of keeping a lid on his emotions, but that lid would occasionally come off in the biggest moments, and it did just that here as he jumped into the air and let out a roar on match point, making it abundantly clear how much the win meant to him.
It wasn't a win that would reignite his career as many would have hoped, proving to be his last-ever victory at the ATP Finals and his last over Djokovic, or any other top player for that matter.
He'd spend most of the two years that followed on the sidelines trying to recover from a knee injury. While he did pick up some memorable wins, making it to the semi-finals of the 2020 Australian Open and the quarter-finals of Wimbledon in 2021, his physical issues meant that he'd never be anywhere near his best again.
The history books will show that the final singles match of his career was a straight-sets defeat to Hubert Hurkacz in that aforementioned Wimbledon quarter-final, with him losing the last of those sets 6-0.
However, the real Roger Federer wasn't playing that day. The real Roger Federer had bid farewell to the sport on a cool November night, 15 miles east, 20 months prior.
And what a farewell it was.
