Wasps became the fifth side to reach the Heineken Cup quarter-finals with a hard-fought win at Castres.

A crucial try from England wing Tom Voyce just after half-time, as well as the reliable boot of Alex King, who kicked 11 points, put the Guinness Premiership side through after they withstood a brutal late surge.

Wasps will host a quarter-final back at Adams Park with a rare away win in Europe, joining Leinster, Munster, Llanelli Scarlets and Biarritz, in the last eight

King dropped a goal and landed two penalties in the opening exchanges as Wasps raced into a 9-0 lead after 15 minutes, but Castres clawed their way back into the game with fly-half Cameron McIntyre landing two penalties to close the gap.

But the French side suffered a blow when New Zealander McIntyre was carried off with a broken ankle just before the break, which paved the way for former Scotland number 10 Gordan Ross to take over the kicking duties.

He got off to an auspicious start - both of the former Leeds Tykes' penalty attempts fell short of the mark, which left Wasps 9-6 up at half-time.

Wasps had some good fortune just after the break when a Castres attack was broken when Simon Shaw swatted down a pass and hooker Ralph Ibanez quickly led a counter-attack.

The ball was moved wide which stretched the home defence before wing Voyce had the ball knocked into his hands by a Castres defender and the flier sprinted under the posts.

King had no problems landing the simple conversion and Wasps were 16-6 clear with half an hour to play.

But the French response was swift as they battered the visitors' line with several chances for their backs to break the Wasp defence.

But it was the Castres forwards who muscled their way over as lock Pascal Pape was shunted over the line by his pack for a try and Ross banged over the conversion to put the home side back in contention at 16-13.

The last 10 minutes was all Castres as they mounted a furious assault on the Wasps line, but the yellow-and-black line held firm, despite the constant pressure from the desperate home side.

England flankers Lawrence Dallaglio and Joe Worsley put in some huge tackles to deny the hosts and although Castres picked up a bonus point for the narrow defeat.

Despite their heroics, the French are out of the competition - their 16-point tally is not enough to progress as one of the two best second-placed sides.