Wasps celebrated Lawrence Dallaglio's return to action with a ruthless victory over Cardiff to leave themselves in pole position to qualify for the Powergen Cup semi-final jamboree at the Millennium Stadium.

Dallaglio was making his first start since breaking his ankle four months ago in the opening game of the Lions tour of New Zealand - and he was straight back in the groove as Wasps turned in a dominant, clinical performance.

The Premiership champions led 20-0 at half-time thanks to tries from Ben Gotting and Paul Sackey. Josh Lewsey roared home for Wasps' third just four minutes into the second half.

The Blues hit a purple patch and ran in three tries in the space of seven second-half minutes - from Chris Czekaj, Xavier Rush and Maama Molitika - to move from 33-0 down to within two converted scores.

But James Brooks killed off any hopes of a Cardiff comeback with Wasps' fourth try to secure the bonus point.

Ian McGeechan's men, who beat London Irish last week, top Pool B with nine points with Saracens to play in the final round on December 4.

Cardiff must beat London Irish next and hope for a favour from Saracens to stand any chance of reaching semi-final day in their home city.

The Blues had arrived in High Wycombe on the back of a convincing 37-20 victory over Saracens last week and boasting 2005 Lions Tom Shanklin, making his first start of the season, and Martyn Williams plus Wales Grand Slam winners Rhys Williams and Robert Sidoli.

But Wasps paraded their own galaxy of stars - Joe Worsley, Jonny O'Connor, Matt Dawson and Lewsey all started - and Dallaglio completed the full game.

Tom Voyce - England's forgotten man - shone at full-back in place of red rose new-boy Mark Van Gisbergen, who started the evening on the bench.

Voyce cleared Wasps' lines with perfection, he was safe under the high ball and he proved a constant thorn in Cardiff's side.

It was Voyce's burst onto Fraser Waters' delightful pass that helped set the early tempo in Wasps' favour. The fifth-minute move came to nothing - Voyce's attempted pass over the top was intercepted - but Wasps had issued a telling warning to Cardiff.

Alex King then charged down Nicky Robinson's attempted clearance and was hauled down off the ball by the Welsh fly-half. Robinson, who could have been sin-binned for a professional foul, was fortunate just to concede the three points.

Cardiff were creaking and eventually Wasps fashioned the inevitable breakthrough when Sackey popped the ball off the deck to on-rushing hooker Gotting.

Cardiff pushed for a response but wasted a five-metre scrum and soon fell further behind as King slotted a second penalty.

And in the last minute before half-time Wasps ruthlessly swept 20-0 ahead when Voyce shovelled the ball to Sackey in space on his outside and the former London Irish winger beat the covering defence to slide over for his second try of the season.

Things did not get much better for Cardiff after the interval. The half was only four minutes old when Robinson had another kick charged down - but this time by his own team-mate, lock Deniol Jones - and Lewsey, quick as a flash, burst onto the loose ball and ran in Wasps' third try.

King slotted the afters for a personal haul of 12 points before being replaced by James Brooks.

Van Gisbergen, on as a blood-bin replacement for Voyce, slotted a simple penalty shot as Wasps hit the 30-point mark with 24 minutes remaining.

Van Gisbergen landed a second penalty to extend Wasps' lead further before a stitched-up Voyce returned to the fray.

Cardiff finally found their claws in the last quarter, sparked into action by a solo try from winger Czekaj who chased down his own chip forward.

Rush touched down two minutes later and Wasps then lost Raphael Ibanez to the sin-bin as their defence became increasingly frantic.

Molitika completed an astonishing seven minutes for Cardiff, but the Blues had left themselves too much work to do and Brooks rounded off the evening with the try to seal the bonus point.