Johnny Sexton scores 24 points and comes through unscathed on his first appearance since March. The European champions win 82-8 in the blistering heat of Bordeaux

The green army marched on Stade de Bordeaux and saw Ireland crush Romania with a 12-try record rout. Their Rugby World Cup campaign is up and running.

Victory was always going to be a formality for the world’s No 1 ranked team and they had the try bonus point wrapped up after 33 minutes and an out-of-sight 33-8 lead by half-time.

There were try doubles for Tadhg Beirne, Bundee Aki, Johnny Sexton and Peter O’Mahony as Ireland recorded their biggest World Cup win. It eclipsed the 64-7 rout of Namibia in 2007.

“Fifteen green mirages shimmering in the heat,” said commentator Martin Gillingham. And it surely felt more for Romania as they were left chasing shadows. Ireland kept playing till the end, Beirne’s second try after the hooter stemming from a counter-attack on their own line.

Ireland crush Romania with record score

Johnny Sexton celebrates with Conor Murray after scoring Ireland’s eighth try (Sportsfile/Getty Images)

For Ireland, the match was less a walk in the park and more a run in the sun – sweltering sun, because the temperature hit 36 degrees. “They must be absolutely blowing,” said pundit Brian O’Driscoll in the ITV Sport studio.

The European champions got a shock in the second minute as Sexton’s grubber kick, targeted for Keith Earls, was intercepted and run back for a stunning try by Gabriel Rupanu. The scrum-half rather spoiled the moment by missing the conversion from in front of the sticks.

Related: Watch Romania stun Ireland with try after two minutes

Romanian elation proved short-lived as Jamison Gibson-Park replied within two minutes, Ireland flooding through for the scrum-half to take the scoring pass.

Hugo Keenan was next on the scoresheet as Ireland worked through the gears, their support lines and tip-on passes stretching their opponents to breaking point.

Beirne got the third after long passes by Sexton and James Lowe, and the impressive Aki the fourth in a move that featured a back-of-hand flip pass by prop Andrew Porter.

Sexton’s first try moments before the break caused momentary consternation as centre Jason Tomane slid in as Sexton touched down the ball. Ireland’s captain and talisman, making his first appearance for six months after injury and suspension, clutched his hand as if hurt but he picked himself up to slot over the extras.

Those last two tries came with Romania reduced to 14 men after full-back Marius Simionescu was yellow-carded for an offside infringement near the Oaks’ line.

Life didn’t get easier for the Rugby Europe Championship side as they tired quickly in the second period. Hooker Rob Herring crashed over from a tap penalty, then O’Mahony was on hand for try number seven after Lowe’s run exposed some wilting defence.

Romania held out for 13 minutes before Sexton notched his second try, bursting onto Conor Murray’s pass on a hard line from the ruck. His conversion gave him 24 points – two tries and seven conversions – and equalled the record for most points in a World Cup game by an Irishman. David Humphreys amassed the same number against Argentina in Lens in 1999.

France v Romania

Ireland supporter Eoin Clarke, from Dublin, before the Pool B encounter in Bordeaux (Sportsfile/Getty)

Sexton took his leave after 65 minutes, giving Jack Crowley the opportunity to close things out. The skipper walked off to a huge ovation from the 25,000 Irish fans in the stadium.

Mack Hansen, a late addition to the bench after Robbie Henshaw was withdrawn as a “precaution”, gave a nice pop pass for Aki to thunder through for his second try. O’Mahony also got his second and there was a try for young lock Joe McCarthy, who had earlier been held up over the line by Vaovasa. O’Mahony was named Man of the Match.

Crowley kicked impeccably off the tee and the score mounted. “Putting 80 points on the board, we’ve got to be happy with that,” said head coach Andy Farrell following a match that extends Ireland’s record winning run to 14. They have won 26 of their last 28 Tests.

Ireland will be satisfied by their afternoon’s work but not overly so against limited opposition. Their lineout didn’t function well and that is a key area in need of improvement as Farrell’s team look ahead to sterner challenges.

“We know there’s a much tougher task on Saturday against Tonga,” said the 38-year-old Sexton, who with 1,074 points is rapidly closing in on Ronan O’Gara’s record as Ireland’s highest scorer in Test rugby (1,083).

Ireland Hugo Keenan; Keith Earls, Garry Ringrose, Bundee Aki, James Lowe; Johnny Sexton (capt), Jamison Gibson-Park; Andrew Porter, Rob Herring, Tadhg Furlong, Joe McCarthy, James Ryan, Tadhg Beirne, Peter O’Mahony, Caelan Doris.

Replacements 16 Ronan Kelleher, 17 Jeremy Loughman, 18 Tom O’Toole, 19 Iain Henderson, 20 Josh van der Flier, 21 Conor Murray, 22 Jack Crowley, 23 Mack Hansen.

Romania Marius Simionescu; Nicolas Onotu, Jason Tomane, Fonovai Tangimana, Tevita Manumua; Hinckley Vaovasa, Gabriel Rupanu; Iulian Hartig, Ovidiu Cojocaru, Alexandru Gordas, Adrian Motoc, Stefan Iancu, Florian Rosu, Vlad Neculau, Cristian Chirica (capt).

Replacements 16 Florin Bardasu, 17 Alexandru Savin, 18 Gheorghe Gajion, 19 Marius Ifimiciuc, 20 Dragos Ser, 21 Alin Conache, 22 Tudor Boldor, 23 Taylor Gontineac.