Cardiff Blues marched into the semi-finals of the EDF Energy Cup thanks to a dominant forward display and some tigerish defence when the Irish hit back in the third quarter.

With the renowned Irish lineout rarely functioning, the Blues had an abundance of possession but the visitors, with flanker Steffon Armitage outstanding, never gave up.

The Welsh team were totally in control of the opening period, only handling errors and wrong options preventing them building a bigger lead.

A knock-on from the kick-off gave young Irish fly-half Shane Geraghty a drop goal opportunity, which he put wide, but it was the home team who blew a perfect chance to take the lead.

Australian centre Marc Stcherbina made a superb break, only for his pass to flying Fijian Mosese Luveitasau to be a yard forward and the winger's sprint to the line was in vain.

It looked a costly mistake when the Exiles' own Welshman, scrum-half Richie Rees, raced away from a tapped penalty.

The former Osprey found wing Justin Bishop, who stepped inside opposite number Chris Czekaj to score and Geraghty converted.

The Blues' constant assaults were rewarded with three almost identical penalties from Kiwi full-back Ben Blair, before they finally broke the stubborn Irish resistance.

Superb flanker Martyn Williams sold a huge dummy to Geraghty and darted between him and lock Bob Casey and Blair then converted.

Mike Philips and Williams were held up on the line before Czekaj claimed the Blues' second try just before the break.

The winger chased his own kick ahead and, despite being obstructed, grabbed the touchdown as the ball bounced away from the covering defenders.

The Irish, needing a bonus point victory to go through, went for position rather than the posts, but their inability to hold on to the ball in the tackle cost them dearly.

There was a scare for the home fans when Nicky Robinson had a clearance kick charged down on his own line, but the Blues fly-half somehow managed to get his hands on the loose ball first.

A cross kick by Geraghty for Bishop was a foot too long, but the Irish kept hammering away, although the wet ball was proving difficult for both sides to deal with.

Blues prop Gethin Jenkins almost made the line from an interception, while the visitors were twice forced to touch down behind their own line, yet somehow kept the Welsh region at bay.

Barry Everitt replaced Geraghty and added penetration to the Irish attacks, but the Blues came nearest to scoring when Luveitasau was just beaten to his own kick by Samoan Sailosi Tagicakibau.

The Irish lost centre Seilala Mapusua to the sin bin for a deliberate infringement in front of his own posts and the offence was doubly punished when Blair slotted the easy penalty and put the result beyond doubt.

There was worse to come, however, with an injury-time cross-kick by Robinson giving the unmarked Czekaj a simple second try and Blair's touchline conversion merely rubbed it in.