Grigor Dimitrov became the first debutant to win the ATP Finals since 1998 after besting David Goffin 7-5, 4-6, 6-3 in a high-quality final.
Perhaps the unlikeliest final line-up in the 47-year history of the ATP's season-ending finale, 2017's edition was the first time that neither participant had previously reached a Grand Slam final in their careers.
But both men combined to produce a contest worthy of the occasion, with this encounter a far cry from Dimitrov's 6-0, 6-2 win over Goffin during the round robin stage.
After that chastening experience, Goffin had gone on to comfortably beat Dominic Thiem and then stun Roger Federer in the semi-finals, with the Belgian visibly unleashing on his groundstrokes against the Swiss.
And following a tight opening period which saw three successive breaks of serve, Goffin returned to that free-hitting state of mind to move into a 4-2 lead, and looked by far the more comfortable player.
But roared on by the vast Bulgarian contingent packed into the o2 Arena, Dimitrov recovered from a nervous start, squaring things up for 4-4 before moving 5-4 ahead, showcasing his at times scarely-believable athleticism en route.
Goffin served out to stay in the set, but Dimitrov got the crucial break at 6-5, eventually overcoming his opponent's stout resistance to convert his fifth set point.
Given his remarkable exertions throughout the week, not least coming from a set down to beat Federer, one had to wonder just how much Goffin had left in the tank.
Dimitrov had the opportunity to establish an authoritative lead when he forged a break point at 3-3, but Goffin saved it with an inch-perfect backhand winner before promptly breaking the Bulgarian's serve in the next game, and would consolidate for a 5-3 lead.
The Bulgarian was proving to be his own worst enemy at times, and while he did produce a sublime flicked backhand en route to holding for 4-5, Goffin served out to love to force a decider.
Now in the ascendancy, Goffin teed off on Dimitrov's opening service game in the third set, but saw two break points go begging. Next, it was Dimitrov's turn to squander an opportunity, failing to convert a break point of his own.
But the Bulgarian was beginning to get back into the groove, and grabbed the crucial break at 3-2 in an 11 point game when Goffin dragged a backhand into the sidelines.
Energised by that breakthrough, Dimitrov waltzed through a quick hold before setting up three match points by rampaging to 40-0 on Goffin's service.
But the Belgian has been nothing if not resilient this week in London, and he extended his ATP Finals campaign by one more game after fending off all three break points to ask the serve out question of Dimitrov.
In the final game, another match point went unconverted with Dimitrov leading 40-15, but the Bulgarian claimed the biggest title of his career when Goffin sliced a volley into the net.
"It’s such an honour to play here. This has been one of the best weeks I’ve ever had," said Dimitrov, who will finish 2017 as the world No.3 after his exploits in London.
"This makes me even more locked in, more excited about my work, and for what's to come.
“It's a great platform for me to build on for next year. It's going to be amazing in the off-season. I know what I have to do in order to do good.”
The result caps a career-best season for the Bulgarian, who in 2017 has more than lived up to the expectation levels thrust up on him. There will be no rest yet for Goffin, though, with the Belgian set to represent his country in the Davis Cup final against France next weekend.
"I proved to myself that I'm in the right place, and I deserve to be here in this tournament," said Goffin after the final.
"Then match after match, I took more confidence until the final.
“So I'm proud of what I've achieved, even if I'm disappointed about the final"