LONDON (Reuters) - Daniil Medvedev barged to the head of the queue of young pretenders as the Russian captured the biggest title of his career by beating Dominic Thiem 4-6 7-6(2) 6-4 in an absorbing climax to London’s last ATP Finals on Sunday.Thiem was on course to become the first Austrian to win the title, following on from his recent U.S. Open triumph, but the relentless Medvedev turned the tide to strike a blow for the new generation striving to shake up the tennis hierarchy. There was no big celebration as he fired an unreturnable first serve on match point to end the two hours and 42 minutes scrap, bringing the curtain down on 12 memorable years at the O2 Arena before Turin takes over as host of the tournament. Fittingly the London era ended as it began with a Russian winner after Nikolay Davydenko took the 2009 title. Sadly for an event that attracted 2.8 million fans over the years to the Thames-side arena, the finale, a vintage edition, played out in a silent arena because of the COVID-19 pandemic.But the millions watching on TV will have appreciated the skill of Medvedev, who became only the fourth player in ATP history to beat the world’s top three at the same tournament. He joins David Nalbandian (Madrid 2007), Novak Djokovic (Montreal 2007) and Boris Becker (Stockholm 1994). “It’s amazing,” Medvedev, who earned $1.56 million as an unbeaten champion, told reporters. “I beat Novak (in the group), Rafa in the semis and Dominic, the best players in tennis right now. It shows what I’m capable of.”Medvedev’s imaginative game, a blend of sledgehammer power, cunning angles and unreadable serving, proved beyond Djokovic in the group phase and then second-ranked Rafael Nadal in Saturday’s semi-final. The 27-year-old Thiem appeared to have mastered it but ultimately was overwhelmed. “I think Dominic was a little tired in the third set and to make him tired in a three-set match is tough,” Medvedev said. His triumph came a year after a chastening three defeats on his debut. The only other player to achieve such a drastic turnaround is Djokovic in 2008.After such a hot streak, including claiming this month’s Paris Masters, the Moscovite was due a dip and it arrived 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. It proved enough for Thiem 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 tough though, saving break points at 2-2 and 3-3, and began to look menacing as the tiebreak arrived.Thiem led 2-0 but Medvedev reeled off seven points in a row to ensure London’s farewell would go the distance. Thiem, who had also beaten Nadal and Djokovic this week, had spent two more hours on court than Medvedev to reach the final and his silky game began to fray. Medvedev stalked him with his power and accuracy and the Russian secured the vital break of serve at 2-2 with a stealthy approach and volleyed winner. Thiem dug in but world number four Medvedev never looked like letting his lead slip as he became the fifth successive first-time winner of the title. Slideshow ( 5 images ) Medvedev’s peers Alexander Zverev, 23, and Stefanos Tsitsipas, 22, won the last two titles here but neither have gone on to claim a Grand Slam. Medvedev will enter 2021 as the man most likely to make that breakthrough for the much-hyped next generation. “For tennis there are exciting times coming,” Thiem said of the new vanguard. “Super important for the sport in general.”