Jonny Marray and Freddie Nielsen recaptured the form that earned them a shock Wimbledon doubles title to win a thrilling ATP World Tour Finals opener.
The British-Danish pairing saved two match points to beat Indian fifth seeds Mahesh Bhupathi and Rohan Bopanna 6-4 6-7 (1-7) 12-10 at London's O2 Arena.
Second seeds and defending champions Max Mirnyi and Daniel Nestor won the opening Group B match on Monday.
Marray and Nielsen are potentially playing their last tournament together.
The Dane wants to concentrate on singles in 2013, saying afterwards: "I see myself as a tennis player. I'm not a singles or a doubles player. I'm not prepared to sacrifice one thing for the other."
The 31-year-old Marray became Britain's first male doubles champion since 1936 this summer and he made history on Tuesday as the first native-born Briton to play in the doubles at the season-ending championships.
He and Nielsen, 29, were playing only their 13th match together, having won just two of six matches when able to link up since Wimbledon, but the big stage clearly agrees with them as they impressed on their ATP Finals debut.
"It's tough to compare it to any other tournament," Marray said.
"I suppose Wimbledon is the only other one, for me anyway, this kind of size with this amount of people supporting you and everything. I'm enjoying every minute of it.
"I'm obviously a bit nervous before going on court every time. I actually felt pretty comfortable out there. I think it helps having Freddie, who is a good friend, out there with me. He's a relaxed character as well."
Asked how his search for a new doubles partner is progressing, the Briton added: "I'm not really set with anyone next year, I'm still on the lookout for a regular partner.
"It's not bearing any fruit as of yet. We'll see how the next few weeks go."
In front of 17,000 spectators, the eighth seeds edged their far more experienced opponents at the key moments to give themselves a great chance of reaching the semi-finals as one of the top two teams in their group.
After failing to trouble Bhupathi and Bopanna in their opening four service games, three fizzing returns earned two set points for Marray and Nielsen and another superb effort off a second serve from the Briton clinched the first set.
The second set was similarly tight, and again the spotlight fell on Marray when he had a match point on the return at 5-4, but agonisingly he could only catch the tape with a forehand.
Bhupathi and Bopanna then showed their class by racing through the tie-break, and then powering into a 5-1 lead in the decisive match tie-break, but the Wimbledon champions worked their way back into the contest.
Teetering on the brink of defeat they saw off two match points, the second in dramatic style as Marray got the better of a quick-fire exchange at the net, and when a double-fault offered Nielsen a second match point, the Dane duly served out for another stunning win.