Andy Murray proved his worth as the one to beat in men's tennis as he outlasted John Isner 6-3 6-7 (4-7) 6-4 to win the Paris Masters.
Murray secured his ascent to the top of the ATP rankings on Saturday after Milos Raonic's withdrawal sent him to the final of this tournament, and he will become world number one on Monday basking in the glow of a fourth straight title triumph.
The ATP World Tour Finals will give Murray the chance to consolidate top spot, and he ended the regular season in ominous form, continuing his personal dominance over Isner with an eighth win from as many meetings.
Murray thrashed Isner in Vienna last week to such an extent that he felt the need for further testing on the practice courts afterwards and, though the American proved sterner opposition here, he was still beaten.
Isner was sharpest out the gate and ought to have opened up break point at 2-2, but he netted from close range after manoeuvring Murray magnificently.
The warning spurred Murray into action and, when Isner double-faulted at 30-30 in the next game, the Scot produced an outrageous return to a typically booming serve, before outlasting the American to move ahead.
Isner then had two break points when he drilled a second serve back from where it came at 165km/h, but Murray's big-game mentality came to the fore, returning two Isner shots that ought to have been winners and holding.
Murray brought the Paris crowd to their feet with a backhanded, cross-court winner on the stretch to get game nine started in style, before efficiently closing it out.
An epic eighth game in a previously sedate second set saw Murray wipe out a 0-40 lead for Isner, before saving a fourth break point to hold, extending the American's career break-point record against Murray to an eye-watering 1/40.
Serve dominated again to prompt a tie-break, where Isner reached 100 aces for the week before eking a mini-break thanks to Murray double-faulting and deservedly consolidating the set with a crunching wide forehand.
Both men looked exhausted in the final set of the 2016 Tour and Isner had to dig deep to save consecutive service games from 30-40 down, but Murray persisted and another close-range fault at the net handed the game's new ruler match point, which he converted thanks to the stunning defence which has helped him scale the heights of tennis.