Biarritz 9-16 Harlequins By James Standley BBC Sport Harlequins made it six Heineken Cup wins out of six as the Pool One winners splashed their way past Biarritz in a game played in driving rain.
Dimitri Yachvili kicked the hosts into the lead in south west France but Nick Evans levelled with a penalty.
Tom Guest raced over from the tail of a line-out and Evans's conversion gave Quins a 10-3 half-time lead.
Biarritz cut the gap with two Yachvili penalties but two more Evans kicks saw Quins secure a gritty victory.
Harlequins went into the game knowing they were already sure of a home quarter-final and the win means they may qualify as top seeds, depending on results over the rest of the weekend.
The English champions pride themselves on their fast-paced attacking game, but that was never going to be possible at a sodden Parc des Sports Aguilera.
Instead they had to dog it out on the Atlantic coast and it was the power of their pack, both around the park and in the scrums, plus a sensible kicking game and a doughty defence, that saw them home.
Quins full-back Brown, here claiming a mark, was superb under the high ball
England man Mike Brown, playing in his usual club position of full-back, was also rock solid under the high ball to help nullify the hosts' favoured method of attack.
Conditions were truly dreadful, with heavy rain falling onto a bog of a pitch that had ponds dotted all over it.
Biarritz could have taken an early lead after Quins infringed when former England full-back Iain Balshaw ran the ball back for the hosts, but Yachvili could not hit the target and looked ruefully at the flooded turf beneath his feet after missing.
However, a Joe Marler indiscretion - the first of many - gave Yachvili another chance and this time the scrum-half drilled the ball between the sticks.
Quins levelled when number eight Imanol Harinordoquy - along with Yachvili discarded by France for the Six Nations - kicked the ball out of Danny Care's hands and Evans bisected the sticks to level matters.
And the hosts took the lead with the game's only try after American flyer Takudzwa Ngwenya knocked on.
Danny Care kicked to the corner and from the resulting line-out the pacy Guest crossed despite Aled Brew's tackle as the Biarritz forwards melted away.
Evans converted and on what was always going to be a low-scoring night, Quins were on their way.
England prop Marler, sin-binned last weekend for fighting, gave away his second penalty and although Quins escaped without conceding any points, at the next scrum Marler and Wenceslas Lauret were yellow-carded after a scuffle in which the Biarritz man appeared to be the aggressor.
The second half turned into even more of a war of attrition, with both sides trying to force penalties for their respective kickers.
Biarritz created two chances for Yachvili, which he duly landed to cut the gap to a point, but Evans drilled over a long-range effort via the centre of the crossbar to take things back out to 13-9.
The hosts forced another chance just after the hour mark but, after being forced to move his kicking tee back several feet because of a small lake, Yachvili pushed it well wide.
And Evans landed a late penalty as the Quins scrum once again got on top to secure victory on a night more suited to the world bog snorkling championships than professional rugby.
Team line-ups
Biarritz: Iain Balshaw; Takudzwa Ngwenya, Benoit Baby, Damien Traille, Aled Brew; Jean Pascal Barraque, Dimitri Yachvili; Fabien Barcella, Arnaud Heguy, Ben Broster, Thibault Dubarry, Pelu Taele, Wenceslas Lauret, Raphael Lakafia, Imanol Harinordoquy (capt). Replacements: Jean-Philippe Genevois, Thomas Synaeghel, Eugene van Staden, Erik Lund, Talalelei Gray, Yann Lesgourgues, Julien Peyrelongue, Seremaia Burotu. Harlequins: Mike Brown; Tom Williams, George Lowe, Jordan Turner-Hall, Ugo Monye; Nick Evans, Danny Care; Joe Marler, Joe Gray, James Johnston, Ollie Kohn, George Robson, Maurie Fa'asavalu, Chris Robshaw (capt), Tom Guest. Replacements: Rob Buchanan, Mark Lambert, Will Collier, Charlie Matthews, Luke Wallace, Karl Dickson, Ben Botica, Ollie Lindsay-Hague. Referee: John Lacey (Ire),
Quins full-back Brown, here claiming a mark, was superb under the high ball
England man Mike Brown, playing in his usual club position of full-back, was also rock solid under the high ball to help nullify the hosts' favoured method of attack.
Conditions were truly dreadful, with heavy rain falling onto a bog of a pitch that had ponds dotted all over it.
Biarritz could have taken an early lead after Quins infringed when former England full-back Iain Balshaw ran the ball back for the hosts, but Yachvili could not hit the target and looked ruefully at the flooded turf beneath his feet after missing.
However, a Joe Marler indiscretion - the first of many - gave Yachvili another chance and this time the scrum-half drilled the ball between the sticks.
Quins levelled when number eight Imanol Harinordoquy - along with Yachvili discarded by France for the Six Nations - kicked the ball out of Danny Care's hands and Evans bisected the sticks to level matters.
And the hosts took the lead with the game's only try after American flyer Takudzwa Ngwenya knocked on.
Danny Care kicked to the corner and from the resulting line-out the pacy Guest crossed despite Aled Brew's tackle as the Biarritz forwards melted away.
Evans converted and on what was always going to be a low-scoring night, Quins were on their way.
England prop Marler, sin-binned last weekend for fighting, gave away his second penalty and although Quins escaped without conceding any points, at the next scrum Marler and Wenceslas Lauret were yellow-carded after a scuffle in which the Biarritz man appeared to be the aggressor.
The second half turned into even more of a war of attrition, with both sides trying to force penalties for their respective kickers.
Biarritz created two chances for Yachvili, which he duly landed to cut the gap to a point, but Evans drilled over a long-range effort via the centre of the crossbar to take things back out to 13-9.
The hosts forced another chance just after the hour mark but, after being forced to move his kicking tee back several feet because of a small lake, Yachvili pushed it well wide.
And Evans landed a late penalty as the Quins scrum once again got on top to secure victory on a night more suited to the world bog snorkling championships than professional rugby.
Team line-ups
Biarritz: Iain Balshaw; Takudzwa Ngwenya, Benoit Baby, Damien Traille, Aled Brew; Jean Pascal Barraque, Dimitri Yachvili; Fabien Barcella, Arnaud Heguy, Ben Broster, Thibault Dubarry, Pelu Taele, Wenceslas Lauret, Raphael Lakafia, Imanol Harinordoquy (capt). Replacements: Jean-Philippe Genevois, Thomas Synaeghel, Eugene van Staden, Erik Lund, Talalelei Gray, Yann Lesgourgues, Julien Peyrelongue, Seremaia Burotu. Harlequins: Mike Brown; Tom Williams, George Lowe, Jordan Turner-Hall, Ugo Monye; Nick Evans, Danny Care; Joe Marler, Joe Gray, James Johnston, Ollie Kohn, George Robson, Maurie Fa'asavalu, Chris Robshaw (capt), Tom Guest. Replacements: Rob Buchanan, Mark Lambert, Will Collier, Charlie Matthews, Luke Wallace, Karl Dickson, Ben Botica, Ollie Lindsay-Hague. Referee: John Lacey (Ire),