NEC Harlequins produced a 30-minute horror show to concede seven second-half tries and crash to their worst-ever Heineken Cup loss at Stade Pierre Antoine.
Quins had only pride to play for in the fifth-round Heineken Pool 4 match, but led 3-0 after 20 minutes and trailed only 8-11 after 50 minutes. But the last half an hour was one-way traffic as the Castres players queued up to score.
The victory moves Castres to 16 points and second place in Pool 4, but they face a daunting trip to the Gnoll ground in Neath next weekend. Sixteen points won’t be enough to qualify as one of the two best runners-up, so coach Christophe Urios’ men need a win in Wales to secure a berth in the final eight for the second time in four seasons.
The game kicked off in perfect conditions at a half-full Stade Pierre Antoine, and Harlequins opened the scoring with an Andy Dunne penalty goal. The diminutive fly-half’s well-struck goal was the only scoring of the opening quarter as the two sides renewed acquaintances between the two 22m lines.
Castres began to take control through the boot of Laurent Marticorena (two penalty goals), and scored the only try of the half through flanker Rodrigo Capo Ortega to take an eight-point lead into the break. 
Quins fullback Gavin Duffy brought his side back to within three points with a well-taken try early in the second half, but the 50-minute mark signalled the start of one of the worst periods in the English club’s history.
Hard-working hooker Remi Vigneaux was first over the line, followed by scrum-half Alexandre Albouy and replacement backrower Romain Froment.
Capo Ortega scored his second before Quins skipper Luke Sherriff stemmed the flow with a five-pointer of his own, but a second try to Froment and one to fellow backrower Guillaume Bernad turned the match into a romp.
In the final minute of the match, former Test winger Ugo Mola snatched an interception and was able to walk the ball across the Quins’ try-line as the Englishmen flagged it away.
The whistle will be blown on Quins’ European participation when they take on Munster at Twickenham next Saturday.