Ireland thrashed Romania 82-8 to get their World Cup campaign started in style in Bordeaux on Saturday, running in 12 tries despite the sweltering heat as the returning Johnny Sexton pulled the strings and centre Bundee Aki ran riot.

Romania briefly led against the No. 1-ranked team in the world, after running back a clearance kick and sending scrum half Gabriel Rupanu clean through to score in the second minute.

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That however was as good as it got for Romania, as Ireland took a stranglehold on the game and racked up tries for Jamison Gibson-Park, Hugo Keenan, Tadhg Beirne (2), Aki (2), Sexton (2), Rob Herring, Peter O'Mahony (2), and Joe McCarthy.

By the time Sexton walked off to a standing ovation midway through the second half the game was long over as a contest.

Rupanu's try stunned the large contingent of Irish fans but delighted the neutrals in the crowd, serving to only spur the Irish into action and they responded within two minutes, before going on to secure a one-sided and record-breaking win.

They were 25 points clear at half-time and will see success, however expected, as a good start to their Pool B campaign, with much tougher tests to come against World Cup holders South Africa and Scotland.

Their backline ran at Romania at every opportunity, and they had their first try in the fifth minute through Gibson-Park, followed by Keenan who went under the poles in the 13th minute.

Beirne, Aki and captain Sexton, back in the team after suspension and almost six months without a game, also dotted down in the first half, with Sexton getting a second just past the hour mark.

Veteran flanker O'Mahony scored two tries in the second half, which started with a tap penalty burst over for hooker Herring and also saw giant lock McCarthy burst over with a dexterous piece of handiwork.

Aki's power was also impressive, running perfectly into the gaps and getting his second try six minutes from time to take the Irish tally past the 70-point mark. Beirne put the cherry on the top with a breakaway deep in stoppage time.

Sexton kicked over seven conversions for a total of 24 points, which equalled David Humphreys' Irish record for points in a World Cup game in the 1999 defeat to Argentina in Lens. Sexton's replacement Jack Crowley kicked over the other four.

The 74-point winning margin was also Ireland's record win at the tournament, eclipsing their 64-7 win over Namibia in Sydney at the 2003 finals.

Ireland next meet Tonga in Nantes next Saturday while Romania return to Bordeaux against South Africa on Sunday, Sept. 17.