DID anyone think they'd see the day when at the end of a ferociously attritional, gut-sapping, backs-to-the-wall, everything-on-the-line sort of game that Leinster would emerge as the last men standing?

Even if the current squad now roll their eyes at every accusation of flakiness and inconsistency, there wasn't much evidence so far this season that the stereotype had been replaced by something more hard-nosed.

The performance of sustained defiance in the quarter-final might have been a sign of Leinster's growing self-belief, but they were up against a Harlequins side which hadn't been there, hadn't done it, and despite a bucket-load of possession, clearly didn't know how to do it. Munster, of course, were going to be an entirely different proposition.

But once Leinster settled last Saturday, and once the juggernaut had a couple of worrying wheel-spins, Ronan O'Gara couldn't get it back on the road. Luxuriating in their Lions' share and in their Magners League success, it was as if Munster had lost a fraction of the steely focus that had made them the most feared side in the tournament.

Their back row was wiped out, both O'Gara and Paul Warwick, who had been so dominant in the tournament's earlier rounds, nosedived badly and with Peter Stringer offering little or no running threat, Tomas O'Leary's abrasive qualities were sorely missed.

Yet, the fall-out from what was an inspiring occasion for Irish rugby both on and off the pitch had more to do with Leinster's all-round excellence and less to do with Munster's failings on the day.

"Winning is what we do this for and while you're always surrounded by doubt, we believed we could win," says Michael Cheika. "I've got to be pretty hard on myself, I won't be soaking any of it up because I understand that we want to win the final. If I let my guard slip for a minute and think like that, then everyone else might let their guards slip for a minute too, and all those minutes add up."

Although there were no frank admissions during the build-up of how devastating a defeat in the image of 2006 would have been for Cheika and his squad, Leinster were playing for their very reputations. Another heavy loss and it would've felt as if three years of hard labour had gone down the drain.

So, there was an urgency and a ferocity that took Munster slightly by surprise, and while the victory was crowned by two sublimely-created tries, the foundation was laid by a monumental defensive performance. Harlequins had been stopped, but Munster were smashed.

The danger for Leinster was that too many of their tackles would be what are called 'soaks' in the trade. In other words, the Leinster defender would just about make the tackle by dragging or pulling the Munster ball-carrier down, but the ball-carrier would still be going forward instead of being knocked backwards.

In the end, they were so aggressive and so organised that 81 per cent of their tackles drove the Munster player back and eight per cent turned out to be soaks. When a 10-per-cent miss total is widely regarded as near to perfect as makes no difference, Leinster missed only 11 per cent.

"We just kept coming, and speed off the line is king in those situations. It's the only thing that's going to stop them," says Kurt McQuilkin, Leinster's defence coach. "You sit on your heels and you wait for a Wallace or an O'Connell to come at you and you're going to be soaking at the very best, and missing at the very worst."

While Cheika, Jono Gibbes and Alan Gaffney are entitled to take a bow for plotting Munster's downfall, McQuilkin's addition to the coaching ticket in 2007 might well have made the crucial difference. Last season, Leinster conceded 11 tries in six Heineken Cup games whereas this season they've conceded just one in their last six. Serge Betsen's try for Wasps at Twickenham in January is the only time their line has been crossed in almost nine hours of European rugby.

If the genial New Zealander has been the architect of Leinster's new defensive edge, the players executed the plan at Croke Park with a burning intensity. Even before Brian O'Driscoll's intercept try ended the game as a contest, there was a moment just after the 50-minute mark when Munster's font of self-belief was visibly reduced to a trickle.

As the red jerseys thundered forward again and again into their opponents' 22, Jerry Flannery had to dig a ball out from the bottom of a ruck. The delivery to David Wallace in the first receiver position was fine, but just as he prepared to take the pass, he had one eye on the ball and one eye on the massed ranks of blue advancing towards him.

"When Wally dropped that pass, we sort of knew we had them on the run," McQuilkin explains. "We'd obviously done our job because they were now looking at us coming at them, and they were taking their eye off the ball not just literally. They were starting to have a second look at us."

Having been filleted at Thomond Park last month, Leinster were switched on to their defensive duties like never before. Right from Felipe Contepomi's kick off when Shane Jennings hammered Warwick and when Rocky Elsom went through with a hit on Lifeimi Mafi, even though the Munster centre didn't have the ball, the winners' intent was obvious.

Once again, the marauding Elsom was involved in much that Leinster did well. When Mafi threw out a terrible pass early in the second half, Elsom half-drove, half-dragged the unfortunate Warwick backwards with an all-enveloping tackle. The way that Warwick seemed to shrink as his Aussie compatriot moved in for the kill was a reflection of Munster's ebbing challenge.

"For me as a foreigner to be involved in that match was a very proud moment. It was such a big day for Irish sport," says Cheika. "We've been criticised and everyone is entitled to their opinion, but you'd be lying if you said the negativity doesn't get to you sometimes. You ask yourself, 'Am I doing the right thing?'. But you have to believe in yourself, we know how hard we work, and now this is where we want to be."

Although Leinster aren't convinced that Munster's failure to convert Keith Earls's scintillating break into a crucial try was a turning point, once again it was another Elsom tackle that got between the European champions and some early momentum.

Elsom's smothering hit on Ian Dowling was less to do with McQuilkin's system and more to do with his own instinct for danger. As Earls was first slowed by Luke Fitzgerald and then grounded by Isa Nacewa, Elsom gambled on staying wide rather than being drawn to the breakdown, and the gamble paid off even though he was a yard offside when he charged into Dowling.

Leo Cullen made more tackles than he'd expect to make in three games, and so did Cian Healy and Stan Wright. Elsewhere, the decision to start Nacewa at full-back paid off, and when Jonathan Sexton came on he demonstrated the sort of big-game composure he once appeared to lack.

Cheika has mentioned that Leinster got the bounce of the ball, but their overdue victory had little to do with good fortune. This time, the immovable object was driven out of town. "Munster are obviously such a quality team, it makes you happy to beat someone who has beaten you twice this season," the coach reflects. "But you can talk about last Saturday's game and how great it was sometime in the future because it needs to have that accompanying achievement to go with it. And that's to go on and win the tournament."

This one victory, no matter how seismic, won't be enough when the history of this season's tournament is written. If Croke Park is to be seen as a defining moment, Leinster have to do it all again on Saturday week.

mjones@tribune.ie