Gloucester did 'Quins a huge favour in beating table toppers Toulouse, but Conor O'Shea's side blew their chances of reaching the quarter-finals as pool winners as a nightmare scenario played out for them.

Niall O'Connor notched three penalty goals to push Connacht into a 9-5 half-time lead, however the hosts failed to take full advantage of a strong wind.

Sam Smith's eighth-minute try showed Harlequins' capabilities with ball in hand. Nevertheless, a single penalty from Nick Evans was all they could conjure up despite dominating possession and territory after the break.

The visitors elected to play into the elements in the first half, and pressure at scrum time on James Johnston yielded an early penalty which O'Connor stuck it over.

'Quins replied in brilliant fashion, using their big ball carriers to build momentum in the 22 before Evans' flat pass sent Smith diving over in the left corner past Fetu'u Vainikolo's limp challenge.

Evans had to improvise after the ball fell off the kicking tee during his run-up, drop-kicking his conversion which spiralled wide in the difficult wind.

Johnston was pinged for another binding offence when play resumed, allowing O'Connor a long range shot which he sent over with aplomb.

Despite being starved of possession, Connacht went 9-5 ahead when O'Connor swung over a left-sided penalty after some mishandling from 'Quins.

In a tense second quarter, Connacht survived a couple of five-metre scrums but they failed to get their attack going - forcing passes as they tried frantically to take advantage of an increasing wind.

Connacht enjoyed some late territory, a close range surge from Mike McCarthy helping to set up O'Connor's fourth shot at goal - yet the out-half managed to screw his easiest kick to the right and wide.

It was all Harlequins when the second half got underway, Ugo Monye just failing to hold onto Evans' bouncing grubber kick as Connacht's defence was immediately tested.

Connacht maintained a high tackle rate, with a doughty scrum and feisty work in contact from man-of-the-match John Muldoon and McCarthy continuing to frustrate O'Shea's charges.

Having turned down an earlier kickable penalty, Evans was called upon to add three points to the 'Quins tally after Muldoon infringed at a ruck.

The New Zealander did just that, making it a single-point game with 20 minutes left on the clock. It seemed enough time for the English outfit to prevail.

They had the upper hand in the scrum. Another good shunt, 13 minutes from time, gave Evans the opportunity to kick 'Quins ahead, but the Kiwi misjudged the wind and Connacht drew breath.

Energised by their ability to hold onto that slender lead, Connacht edged closer to their first Heineken Cup win thanks to a combination of sterling work up front and unforced errors by 'Quins.

Danny Care and company were unable to find space against a tiring but suffocating Connacht defence, with Eric Elwood's men holding their nerve to end a losing run which stretched back to September.

Irish eyes were smiling on the double as the results in Pool 6 have sent Connacht's provincial rivals Ulster through to the last-eight, in advance of their final pool game against Clermont Auvergne.

Speaking after such a memorable night for rugby in the west, Elwood said: "Even with the last scrum with nine seconds left I still wasn't convinced until the ref had blown the whistle and the ball was off the park, and people were invading the pitch.

"Unfortunately in Connacht we don't make things easy, but i have to acknowledge the commitment of the boys.

"A silly try by our standards and even leading by four points with the elements in their favour, to defend like we did with the discipline we did, the commitment was excellent.

"And even to get within one point, Harlequins would have felt they would push on. Our tackle count was two or three times (what theirs was), but that's nothing new for us.

"I think everyone got their reward tonight - the players and the crowd, and it was not the prettiest of games - but at the and of the day we have been knocking on the door for the last 13 weeks so I am quite happy to take an ugly win, no problem."

Elwood praised his troops for the persistence they have shown throughout their run of bad results, and hopes that they can now take confidence from this win into the RaboDirect PRO12.

"Some of these players having been playing 80 minutes for the last 13 weeks and it's a credit to them. It's fantastic. We've been minding them during the week so they can play on a Saturday and they deserve great credit for it.

"What this (result) means is that we have the monkey off our backs. The lads now know that against one of the better teams of Europe we can grind out a victory if we need to, but to do that you have to do the simple things right.

"The attention to detail is massive and we have to keep up that enthusiasm and passion and commitment that we had tonight.

"We didn't play a lot of rugby tonight because we didn't have the ball, and to win a big game in Europe against that quality, the lads will be able to take a lot of heart from that into the remaining games of the league."