Harlequins finished the Heineken Cup pool stages unbeaten thanks to a 16-9 win over Biarritz in horrendous conditions at Parc des Sports Aguiléra on Friday.
In driving rain and on a sodden pitch, Quins became only the second team to win in Biarritz in the Heineken Cup in 12 years and the first since Cardiff in 2008.
The result leaves the English champions on 27 pool points and provisionally the top seeds going into the quarter-finals.
For Biarritz, a losing bonus point might not even be enough for them to have a chance of defending their Challenge Cup title.
Harlequins led 10-3 at half time thanks to a try from back-row Tom Guest and a handful of second-half penalties from Nick Evans proved enough for victory.
Biarritz looked sure to score first with a powerful driving maul early on, only to see Olly Kohn rip possession away within touching distance of the whitewash.
Dimitri Yachvili did eventually open the scoring from the kicking tee but Evans replied to leave the scores locked at 3-3 until the half-hour mark.
Guest put the visitors in front with the first try of the night when he took a line-out and found no one in his was way when he came down to earth. The number eight bolted to the line to score an unlikely try to which Evans added the easy extras.
A dust-up between Wenceslas Lauret and Joe Marler ended with both the Biarritz flank and the Quins prop seeing yellow, but it made no difference to the domination enjoyed by the English club's scrum.
Yachvili reduced the gap to a single point early in the second half with two penalties but Evans answered will a fantastic long-range effort to leave the scores at 13-9 going into the final quarter.
Yachvili sent his next attempt wide but Evans made no mistake with his third penalty to restore the seven-point lead as time ran out.
Pens: Yachvili 3
Yellow card: Lauret
Pens: Evans 3
Yellow card: Marler
Biarritz: 15 Iain Balshaw, 14 Taku Ngwenya, 13 Benoît Baby, 12 Damien Traille, 11 Aled Brew, 10 Jean-Pascal Barraque, 9 Dimitri Yachvili, 8 Imanol Harinordoquy, 7 Raphael Lakafia, 6 Wenceslas Lauret, 5 Pelu Taele, 4 Thibault Dubarry, 3 Ben Broster, 2 Arnaud Heguy, 1 Fabien Barcella.
Replacements: 16 Jean-Philippe Genevois, 17 Thomas Synaeghel, 18 Eugène Van Staden, 19 Erik Lund, 20 Talalelei Gray, 21 Yann Lesgourgues, 22 Julien Peyrelongue, 23 Seremaïa Burotu.
Harlequins: 15 Mike Brown, 14 Tom Williams, 13 George Lowe, 12 Jordan Turner-Hall, 11 Ugo Monye, 10 Nick Evans, 9 Danny Care, 8 Tom Guest, 7 Chris Robshaw (c), 6 Maurie Fa'asavalu, 5 George Robson, 4 Olly Kohn, 3 James Johnston, 2 Joe Gray, 1 Joe Marler.
Replacements: 16 Rob Buchanan, 17 Mark Lambert, 18 Will Collier, 19 Charlie Matthews, 20 Luke Wallace, 21 Karl Dickson, 22 Ben Botica, 23 Ollie Lindsay-Hague.
Venue:Parc des Sports Aguiléra
Referee: John Lacey (Ireland)
Assistant referees: Paul Haycock (Ireland), Michael Black (Ireland)
Television match official: Seamus Flannery (Ireland)