Daniil Medvedev came from a set down to beat Dominic Thiem 4-6, 7-6 (7/2), 6-4 and win the ATP Finals title in London on Sunday. A single break was enough for Thiem to win the first set but the Russian fourth seed dominated the second-set tie-break to level the match and secured the decisive break in the fifth game of the decider. jw/dj