Wales wonder-kid James Hook scored a brilliant solo try as the Ospreys eased into this season's EDF Energy Cup semi-finals by brushing aside Liberty Stadium visitors Bristol.

The 21-year-old's spectacular effort showcased his mesmeric running skills and sparked an Ospreys points spree after they led just 10-3 at half-time.

Hook, whose nerveless kicking underpinned an impressive Wales fightback to earn a draw against Australia last month, also slotted three conversions and a penalty as Bristol conceded three tries in 10 minutes during the third quarter.

Former All Blacks scrum-half Justin Marshall set the ball rolling through an early close-range score, but the Ospreys were inspired by centre Hook, whose flash of inspiration was quickly followed by fellow try-scorers Huw Bennett and Nikki Walker.

And just when Guinness Premiership leaders Bristol thought the Ospreys might shut up shop, Gavin Henson arrived as a 53rd-minute substitute to provide a dangerous presence at fly-half alongside Hook.

Substitute hooker Barry Williams added a fifth Ospreys try during the closing stages, and they join fellow Welsh region Cardiff Blues, English champions Sale Sharks and twice Heineken Cup winners Leicester in tomorrow's draw, with the Millennium Stadium semi-finals scheduled for March 24.

And the prospect - not that Rugby Football Union chief executive Francis Baron would particularly want to contemplate it - remains of an all-Welsh Twickenham final two weeks later.

Bristol boss Richard Hill, knowing his team had little chance of progressing from the group, fielded a second string side with only scrum-half Brian O'Riordan remaining following their 14-12 Premiership victory over Gloucester eight days ago.

Waikato Chiefs recruit Sean Hohneck made his debut though, while Italian Test wing Marko Stanojevic also lined up after scoring six tries in five games for the Azzurri this season.

The Ospreys fielded current Wales internationals Hook, Duncan Jones and Ryan Jones, but Marshall was a surprise starter, given his World XV commitments against South Africa in Leicester, although his late call-up arrived because of sickness suffered by fellow Kiwi Jason Spice.

Hook and Jason Strange exchanged early penalties, before the Ospreys' forward power had a telling impact on 15 minutes as a relentless scrum drive ended when Marshall touched down unopposed.

Hook's conversion opened up a seven-point gap, and there was further misery for Bristol when their Irish hooker David Blaney departed injured to be replaced by Saul Nelson.

Skill levels were poor on both sides, with even Hook - whose confidence levels must be sky high following his autumn Test performances - guilty of complicating simple moves by attempting difficult options that just played into Bristol's hands.

Bristol ended the first period on top territorially, yet they lacked composure under pressure and a well-organised Ospreys defence comfortably kept them at bay.

It took Hook's stunning try to lift the gloom as he danced inside and outside transfixed Bristol defenders from 30 metres out after being freed by fly-half Shaun Connor's pass.

He ghosted past Bristol centres Sam Cox and Josh Taumalolo, then outpaced visiting skipper Craig Short before adding the conversion for good measure.

Bristol were shellshocked by Hook's impudence, and the Ospreys went for the jugular, blitzing their opponents through further quickfire tries for hooker Bennett following a mighty forward surge and then Scottish international wing Walker after he sprinted clear to score in the corner.

Bristol had conceded 17 points in 10 minutes, leaving them facing nothing more than a damage-limitation exercise as the final quarter approached.

With the game done and dusted and Ospreys guaranteed to finish top of Pool A after a second bonus point victory from three EDF games this season, rival coaches Hill and Lyn Jones made an inevitable raft of substitutions.

But there was still time for Williams to complete the rout, adding his team's fifth try and leaving Bristol well beaten.