When Munster went in at half time in Thomond Park Stadium trailing 20-9 they were looking down the very long barrel of a gun. However they delivered a second half performance that justly delivered the narrowest of victories over their great rivals.

They owed much to their pack who recovered from the loss, early in the second of the talismanic Paul O'Connell, and the majestic Ronan O'Gara whose last minute penalty secured a 24-23 victory that leaves them 12 points clear at the top with three games remaining.

Leinster supporters can carp all they want about referee Andrew Small and the influence his 15 penalties against their side had but that would be to ignore the fact that having played second fiddle in the opening half, Munster dominated a second, restricted Leinster to one score and never gave them a sniff of the tryline.

In the end, trailing by two, Munster were hammering away at the Leinster, experiencing fierce resistance, but managed to force the penalty to give O'Gara the opportunity to snatch the win. Cometh the hour, cometh no better man, and the Corkman, from close to the West Stand touchline stroked it nervelessly through the posts.

It just remained for Munster to retain their composure claim the restart and dispatch the ball out of the stadium.

It was an outcome that many, outside the team itself, would have predicted at the end of the opening 40. Leinster led at that stage thanks to five Jonathan Sexton penalties and a try in the 21st minute from Shane Horgan engineered by a searing Isa Nacewa break and then kick to the corner.

And Leinster were full value for that lead having dominated for almost the entire period and started the second half facing 14 after Johne Murphy had been yellow carded in the 35th minute.

O'Gara, mercilessly targeted by the Leinster heavy brigade, departed in the 41st minute to have an eye wound treated and he was followed by O'Connell five minutes later with a serious looking ankle injury. But while O'Gara was off Paul Warwick kicked a penalty and moments after O'Gara returned he landed his fourth successful kick to leave Munster trailing by five.

Mick O'Driscoll slotted in impressively for his injured captain alongside the tireless Donncha O'Callaghan and the Leinster pack were finding their hands full coping with the marauding runs of Damien Varley and the excellent James Coughlan.

Two more penalties, the second a monster from the halfway, edged the home side in front, much to the delight of their vocal supporters but Sexton handed the advantage back to Leinster when he converted his sixth penalty with fifteen minutes remaining.

The groan that went up when O'Gara pushed his 68th minute penalty right and just wide was likely heard in Cratloe but by now Munster tails were up and they had Leinster nicely corralled deep in their own territory.

With time running out, the men in Red laid siege to the Leinster line and in fairness that defence was impressive. It almost begged for O'Gara to drop into the pocket and go for the drop-goal.

But Munster and the man himself seem to delight in dramatic finishes and when they spurned the drop goal option and went wide left, Keith Earls forced the penalty and O'Gara kept that admirable nerve of his.

Munster: F Jones (P Warwick 76 min); D Howlett, J Murphy S Tuitupou 63 min), L Mafi, K Earls; R O'Gara (P Warwick temp), C Murray (P Stringer (67 min); W du Preez (M Horan 67 min), D Varley (M Sherry 76 min), T Buckley (J Hayes 67 min); D O'Callaghan, P O'Connell (capt) (M O'Driscoll 46 min); D Ryan (D Leamy 54 min), D Wallace, J Coughlan.

Leinster: I Nacewa; S Horgan, B O'Driscoll, G D'Arcy, L Fitzgerald; J Sexton, I Boss; C Healy, R Strauss, M Ross; L Cullen (capt), N Hines; K McLaughlin, S O'Brien, J Heaslip. Replacements: A Dundon, H van der Merwe, S Wright, D Toner, R Ruddock, E Reddan, I Madigan, F McFadden.

Referee: A Small (England).