Harlequins director of rugby Connor O'Shea praised his team's attitude in Friday's hard-earned Heineken Cup victory in Biarritz.
The result was only the second home defeat in the last 35 European games for Biarritz as Quins completed a clean sweep in Pool 3 at a soaking-wet Parc des Sports Aguilera thanks to excellent tactical kicking and an opportunistic try from Tom Guest.
Harlequins are guaranteed a home quarter-final and only Toulon and Clermont can now deny them the top seed's spot.
"It was a mature performance and we are delighted with the attitude of the players," said O'Shea.
"There was a lot of experience out there of playing together and in tough conditions but it was one of those nights when you had to roll the sleeves up and show as a group what it means to play for each other. We had to grind it out.
"We knew the kicking duel would be crucial and Nick Evans, Danny Care and Mike Brown kept us playing in the right areas.
"To come to the south of France and get a win against any team is outstanding, especially given that's only the second time in the Heineken Cup that Biarritz have been beaten here.
"That was the motivation for the players as well as aiming to be number one seeds for the quarter-finals which could be important.
"Momentum is great in rugby and it was good to carry on the winning habit. It's also great for the fans who came out to watch us and all those back home who now have something special to look forward to. There's a lot of rugby to be played before the quarter-final but we're looking forward to April."