Roger Federer and Andy Murray started the ATP World Tour Finals after the tournament moved from China to Britain, with both earning opening group victories at the eight-man year-end showcase.
Top seed Federer lost the first set of his career to Fernando Verdasco Sunday, but regrouped after a big effort to defeat the Spaniard 4-6, 7-5, 6-1 in their Group A clash of an event held for the last four years in Shanghai.
Murray lit up the 17,500-strong audience in the darkened hall deep in the far precincts of East London with his opening-day win over Argentine Juan Del Potro 6-3, 3-6, 6-2.
Murray and the US Open champion -- whose form has dived since the day two months ago when he beat Federer in the final -- were the first pair to taste the atmosphere of the new venue.
Federer, who can end the season again on number one if he wins all three of his group matches to hold off chasing rival Rafael Nadal, had his troubles with Spain's Verdasco, coached by a brain trust which also includes Australian Darren Cahill, who turned down a chance to coach the Swiss several seasons ago.
But after dropping the first set after starting with a 3-0 record and six sets won against Verdasco, Federer broke in the final game of the second set as the Spanish armour began to crack.
The top seed and 15-time Grand Slam champion took a 3-0 lead in the final set, ending his fighting victory after just on two hours.
Murray took two hours, ten minutes to secure the opening-day success, with Del Potro unable to overcome a finishing burst from the world number four.
Murray, with an ATP-leading six titles in 2009, secured victory with 30 winners plus early and late breaks in the final set.
His Argentine opponent was undone by 38 unforced errors. Murray converted on five of a dozen break point chances, racing away to a 5-0 lead in the opening set and winning it on his seventh set point.
Mark Knowles and Bhupathi advanced to the next stage in the men's doubles section.
The third seeded pair beat fifth seeds Frantisek Cermak and Michal Mertinak 6-3, 6-3.