Russian Daniil Medvedev has claimed the biggest title of his career, coming back to beat Dominic Thiem 4-6 7-6(2) 6-4 in an absorbing climax to the ATP Finals in London.
Thiem looked on course to add the ATP's prestigious season-ender to his recent US Open title, but 24-year-old Medvedev turned the tide in superb fashion.
The final was a farewell to the tournament for London's O2 Arena, which has hosted it for 12 years - the first edition in 2009 also won by a Russian, Nikolay Davydenko.
Fittingly, Medvedev became the first Russian to win the title since Davydenko and was the most consistent player all week, becoming only the fourth player in ATP history to beat the world's top three at the same tournament.
He outplayed world No.1 Novak Djokovic in the group phase, where he went unbeaten, then outlasted second-ranked Rafa Nadal in Saturday's semi-final, before stopping No.3 Thiem, who finishes as runner-up for the second year in succession.
After an incredible run of form, including claiming this month's Paris Masters, the Moscovite was perhaps due a dip and it happened in the first set, as he threw away a 40-0 lead on serve at 2-2, gifting Thiem a break with a double-fault.
That proved enough for the Austrian to pocket the first set and he went for the quick kill in the second, as Medvedev's usually rock-solid serve and forehand wavered.
The Russian hung in though, saving break points at 2-2 and 3-3, and the set moved into a tiebreak.
Thiem led 2-0, but Medvedev then reeled off seven points in a row to ensure London's farewell would go the distance.
Thiem, who also beat Nadal and Djokovic this week, had spent two more hours on court than Medvedev to reach the final and began to fray in the third set.
Medvedev stalked him with his relentless power and accuracy, and the Russian secured the break of serve he had threatened at 2-2, when he stroked away a volley.
Thiem dug in desperately, but world No.4 Medvedev remained calm to become the fifth successive first-time winner of the title.