|Castres (14) 19|
|Tries: Dupont, Cabannes, Beattie Cons: Dumora 2|
|Harlequins (21) 47|
|Tries: Marler, Walker, Care, Clifford, Lambert, Yarde, Lowe Cons: Evans 6|
Harlequins beat Castres in Pool Two of the European Champions Cup to secure a bonus-point win, but it was not enough to keep their last-eight hopes alive.
Joe Marler and Charlie Walker crossed for the visitors inside 25 minutes.
And a converted Danny Care try gave them a 21-14 interval lead before they ran riot in the second half.
Quins added four more tries, but their efforts were in vain as Wasps clinched a 20-20 draw against Leinster to deny them a quarter-final place.
|European Champions Cup Pool Two|
Castres came in to this fixture on the back of a thumping 50-10 defeat by Leinster in week five, and Harlequins wasted little time in adding to the bottom side's woes.
Requiring at least a bonus-point win, Harlequins set about their task with vigour, Marler crossing after 11 minutes to score the first of the four tries required and Nick Evans successfully kicking the first of six conversions.
Their lead lasted just eight minutes, as a converted Antoine Dupont score levelled the scores, but Walker and Care extended the visitors' advantage.
A Jack Clifford try inside 10 minutes of the second period set the tone for the final 40 minutes, and Quins cut loose after Remi Grosso's 54th minute sin-binning.
Mark Lambert and Marland Yarde made the most of the one-man advantage, running in to extend the Premiership side's lead to 40-14 with 22 minutes remaining.
Nine minutes later, Scotland international Johnnie Beattie took advantage of a poor Quins scrum close to the line, driving over to score a consolation try.
But George Lowe touched down the visitors' seventh try of the afternoon in the dying seconds to leave Quins wondering what might have been.
Harlequins director of rugby Conor O'Shea:
"We could only control what we could control today. You can't rely on others and that's the position we left ourselves in. I thought we played some pretty good rugby in difficult conditions.
"We lacked accuracy last week, despite all the chances we had. Not getting anything out of that game cost us, but Europe is all about learning and our young players have learned an unbelievable amount this season.
"We've gone out by inches, but that's the European Cup for you. We'll learn from it, but we'll also use the hurt to drive us on for the remainder of the season."
Castres: Dumora; Grosso, Combezou, Cabannes, Garvey; Tales, Dupont; Forestier, Rallier, Herrera, Gray, Samson, Faasalele, Caballero, Beattie.
Replacements: Garcia for Dupont (57), Bornman for Faasalele (41).
Not Used: Mach, Fa'anunu, Lazar, Capo Ortega, Lamerat, Kirkpatrick.
Sin Bin: Combezou (40), Grosso (53)
Harlequins: Brown; Yarde, Hopper, Lowe, Walker; Evans, Care; Marler, Gray, Collier, Matthews, Robson, Clifford, Robshaw, Easter.
Replacements: Lindsay-Hague for Yarde (62), Botica for Lowe (28), Marfo for Marler (71), Buchanan for Gray (67), Lambert for Collier (8), Twomey for Matthews (67), Trayfoot for Clifford (69).
Not Used: Dickson.
Ref: Leighton Hodges (Wales).