Jonny Marray and Frederick Nielsen are through to the ATP World Tour Finals last-four after defeating Max Mirnyi and Daniel Nestor in three sets at the O2 Arena in London.
The pair, who claimed the Wimbledon doubles title in the summer, took the opening set via a tie-break, but were overwhelmed in the second, as Mirnyi, a mixed doubles gold medalist from London 2012, and Nestor, an 80-time doubles champion, fought back.
But in the Champions tiebreak, after saving one match point having missed one of their own, Marray and Nielsen kept their nerve to book their spot in the semi-final despite having played just six previous rankings tournaments in 2012.
Having defeated Mahesh Bhupathi and Rohan Bopanna in their opening round robin match, and then seen the Indian pair beat Robert Lindstedt and Horia Tecau in the earlier match, Marray and Nielsen knew just a win against the French Open champions would see them qualify for the knock-out phase on their first appearance at the season ending championship.
And the Wimbledon doubles winners looked well on their way to achieve just that as, after Marray helped save a break point in game six, the following game saw Nestor miss-hit a volley at the net after Nielson's backhand to secure the opening break.
The advantage was short lived however, as Marray, when serving for the set, sent a volley wide to allow Nestor and Mirnyi to restore parity and subsequently take the first set into a tie-break.
While the first mini-break went the way of the eastern-europeans, four points on the trot saw Marray and Nielsen regain control, and with three set points, the victors from the All-England Club in July secured a set advantage.
But if the lottery of the tie-break had favored the leading No.8 seeds, the start of the second set bit back at them as Nielsen served a double fault to hand Nestor and Mirnyi an early lead.
It was an advantage they would keep until the end of the second set, as the world No.2 ranked duo made certain of a champions tie-break third set.
An early break went the way of Nielsen and Marray, as the Dane played a sliced forehand, which evaded Nestor when serving at 3-3, before the Brit's volley crept inside the baseline for a 5-3 lead.
Nielsen's flailing volley should have been punished by Mirnyi, but the Belarusian found the net, before Nestor's neat touch turned the scores around at 7-7.
But Marray found two first serves when required, the second a clean ace, to set up match-point, only for the Liverpool-born player to find the net from Mirnyi's big serve.
It was then the turn of Nielsen to save a match point from Mirnyi and Nestor and then Marray to force an error from the Canadian on the second match point to take the enthralling tiebreak 12-10.
The victory puts the pair into the semi-final in their first visit to the ATP World Tour Finals as they continue to ride on a crest of a wave in the English capital.