All tied up: Tomas O'Leary of Munster struggles to get away from the attentions of Leinster's Jamie Heaslip during last night's Magners League game at the RDS

IF a piece of Brian O'Driscoll genius and a rare example of John Hayes' red mist were the storylines from one more thundering derby, the end-product was a Leinster triumph that was as emphatic as it was unexpected.

O'Driscoll killed the game off with a truly stunning try just after the break, and then Hayes lost his cool and stamped on Cian Healy. A red card was referee Simon McDowell's only option, and surely now a suspension is in the offing for the Ireland tight head. Even if Munster had a full complement, it would still have been Leinster's night. From one to 15, they were magnificent, and their ruthless second-half performance was reminiscent last season's demolition of their great rivals at Croke Park.

Much has rightly been made over the past few seasons of the extraordinary growth of this fixture from a low-key contest for alickadoos into one of the rugby world's seminal rivalries. If the two momentous Heineken Cup semi-finals have predictably caught the imagination to a greater degree than the home-and-away format of the Magners League, this latest chapter would comfortably have filled the 50,000 seats of the new Lansdowne Road had the stadium been open for business.

Paul O'Connell's absence was certainly felt in the opening quarter as Munster went looking for a solid start only to lose their first two line-outs. Jonny Sexton made an early break when he stepped inside Marcus Horan before throwing a speculative pass which was picked off by Keith Earls, and Shane Horgan bustled outside Denis Hurley.

But while Leinster had a perceptible edge as well as the advantage of a stiff breeze at their backs, they would have wanted more than a Sexton penalty on the board by the end of an intensely physical first quarter. Still, the harder exterior cultivated by the home team last season was soon in evidence as Leo Cullen won a line-out and the forwards rumbled menacingly into the 22 more in the image of their opponents. Jamie Heaslip was held up as he surged for the line, but Munster were pinged and Sexton tapped over the simple penalty.

Then we had a truer reflection of Leinster's dominance with the first try of the game courtesy of Gordon D'Arcy. Once more the forwards created the platform in midfield, but in the end, the score could be put down to yet another example of O'Driscoll's class. Spotting a mis-match, he stood up both Denis Leamy and Marcus Horan to put Horgan, who had come in from the right, into space and Horgan calmly delivered the killer pass to D'Arcy. Sexton added the extras to make it 13-0 on 27 minutes.

The margin stayed that way until the interval, however, D'Arcy's effort certainly lit a fire under Munster. Cullen, who had shipped a heavy knock, dropped one ball and the red jerseys streamed out of their half. Leamy then blasted through a previously impervious Leinster defence, yet the visitors butchered the opportunity by needlessly drifting across the pitch. But it was Leinster's half. While not exerting a Rocky Elsom-like influence on the proceedings – who could? – Kevin McLaughlin was going well on his debut in the big time, and with the home side flying into the tackles, there didn't appear to be any reason why they wouldn't hold out.

No reason, in fact, as Leinster made a blistering start to the second half. If O'Dricoll's brilliance in the conception of D'Arcy's try mightn't have been clear to all and sundry, he then produced a moment of sheer genius to put the game out of sight. In fairness, the excellent Eoin Reddan's role in the try shouldn't go unmentioned, but this try was all about O'Driscoll. Accelerating in trademark style onto a pass just outside the Munster 22, he left both Jean de Villiers and Earls for dead with a searing burst.

Sexton's conversion prompted a quick response from the Munster management as both O'Connell and David Wallace were pitched into the fray, and that also seemed to provoke the outbreak of hostilities that left Healy with blood pouring down his face.

Hayes got his marching orders for a stamp on the Leinster loose head, but there were other Munster boots raining down as well. Munster were reduced to 14 men and Sexton landed the penalty to widen the gap even further to 23-0. There were still 25 minutes to go, but Leinster had won the first battle of the season by a mile. Horgan rubbed salt in the wounds with an intercept try five minutes from the end. Round one is over, but thankfully, the war continues.

Leinster I Nacewa; S Horgan, B O'Driscoll, G D'Arcy, L Fitzgerald; J Sexton, E Reddan; C Healy, J Fogarty, S Wright; L Cullen, N Hines; K McLaughlin, S Jennings, J Heaslip Subs Keareny for D'Arcy, 58 mins; M Ross for Healy, 67 mins; Healy for Wright 70 mins; F McFadden for O'Driscoll, 73 mins; M O'Kelly for Cullen and Simon Keogh for Fitzgerald, both 76 mins Scorers D'Arcy, O'Driscoll, Horgan try each; Sexton 3 pens, 3 cons

Munster K Earls; D Howlett, L Mafi, J de Villiers, D Hurley; R O'Gara, T O'Leary; M Horan, D Fogarty, J Hayes; D O'Callaghan, M O'Driscoll; D Leamy, N Ronan, N Williams Subs D Wallce for Williams and O'Connell for O'Driscoll, both 50 mins; Buckley for Ronan, Flannery for Fogarty, both 58 mins; Warwick for Mafi, 64 mins; Dowling for Hurley, 67 mins; Stringer for O'Leary, 70 mins Red card Hayes, 55 mins

Referee S McDowell (Ulster)