Ireland began their World Cup campaign with an emphatic 27-3 win over a ragged Scotland in Yokohama.

The victory sets Joe Schmidt's men on a quarter-final collision course with South Africa, who lost to New Zealand yesterday, in Tokyo on 20 October.

They must first negotiate games against Japan, Russia and Samoa but the heavy lifting has been done with this four-try to nil success over a disappointing Scottish outfit in front of 72,000 fans at the International Stadium.

It was easily the team’s best outing of the year, following on from a disappointing Six Nations and warm-up series, and the call to start Jordan Larmour and Andrew Conway ahead of the more experienced Rob Kearney and Keith Earls proved astute. 

A dominant performance by the forwards, which yielded a perfect set-piece return (12/12 lineouts, 10/10 scrums), paved the way for first-half tries from James Ryan, Rory Best, Tadhg Furlong, with Conway securing a bonus point in the second period. 

Aside from the opening 90 seconds, where Ireland made three unforced errors in a frantic set, the first quarter was practically perfect.

Twice they breached the Scottish 22 and twice they made their main Pool A rivals pay on the scoreboard.

There were just six minutes gone when Iain Henderson broke the defensive line on the 22 and forced Scotland to backpedal.

From there it was vintage Ireland 2018, a patient series of recycling allowed Ryan to burrow over while playing a penalty advantage.

Eight minutes later captain Best forced his way over after a lineout close to the line, with Johnny Sexton off target with the conversion on this occasion.

If the first two scores came straight from the first page of the Schmidt handbook, the third owed a lot to Andrew Conway's kick and chase, the Munster winger forcing the backtracking Stuart Hogg to concede a 5m scrum.

CJ Stander got fast ball at the back of the scrum and prop Furlong was on hand to barge over for his third international try.

The camera cut to the coaches box and Andy Farrell punched the air in delight as Schmidt took a sip of water.

The head coach had spoken about the anxiety that had festered in the camp in the long build-up to this game but that all seemed to dissipate as the half played out.

All Scotland could offer was three points from the boot of Greig Laidlaw but Ireland's dominance on the scoreboard did come at a cost, however.

Peter O'Mahony and Bundee Aki were both replaced, by Jack Conan and Chris Farrell, in the first half after failing Head Injury Assessments, while Sexton twice received treatment for a leg injury and Conor Murray took over the kicking duties.

Scotland, meanwhile, lost busy flanker Hamish Watson to what looked like a tournament-ending knee injury just before the break.

Still there was time for Murray to miss a long-range effort after Scotland were penalised at a scrum but it was certainly a case of so far so good, with the threat of Hogg and Finn Russell largely nullified through well-judged and aggressive linespeed. 

The rain that had been threatened all week eventually arrived for the start of the second half and with that both sides struggled to hold on to the slippery ball.

When Ireland got turned over in their own 22 Scotland couldn't take advantage with John Barclay knocking on close to the line.

The game became stop-start, a pattern that suited Ireland, and Gregor Townsend’s side couldn’t establish any sort of foothold in order to claw their way back into the tie.

Any lingering hopes that they had were extinguished when Conway finished smartly in the corner in the 56th minute, a try that signalled the end of Sexton, Murray and Henderson’s day as Schmidt opted to avoid risking any more key players.

Jack Carty added a penalty in the 68th minute and Ireland had to see out the last 10 minutes with 14 men when Tadhg Beirne was sin-binned for a lazy hand in a ruck but Scotland, who play Samoa on Monday week, couldn’t find any gaps in the line, with replacements Conan (14 tackles) and Farrell outstanding.

Ireland's next game is against Japan in Shizuoka on Saturday where Schmidt will look at his options in preparation for a defining clash with the Springboks in a four weeks’ time.

Ireland: Jordan Larmour, Andrew Conway, Garry Ringrose, Bundee Aki, Jacob Stockdale, Jonathan Sexton, Conor Murray; Cian Healy, Rory Best (capt), Tadhg Furlong, James Ryan, Iain Henderson, Peter O'Mahony, Josh van der Flier, CJ Stander.

Replacements: Niall Scannell, Dave Kilcoyne Andrew Porter, Tadhg Beirne, Jack Conan, Luke McGrath, Jack Carty, Chris Farrell.

Scotland: Stuart Hogg, Tommy Seymour, Duncan Taylor, Sam Johnson, Sean Maitland, Finn Russell, Greig Laidlaw; Allan Dell, Stuart McInally, (capt), Willem Nel, Grant Gilchrist, Jonny Gray, John Barclay, Hamish Watson, Ryan Wilson.

Replacements: Fraser Brown, Gordon Reid, Simon Berghan, Scott Cummings, Blade Thomson, Ali Price, Chris Harris, Darcy Graham. 

Referee: Wayne Barnes