The two-time European Cup winners' 37-14 success at the Stade Aime Giral, aka the bear pit of French rugby, was as stunning as it was unexpected. At the most intimidating of venues where only two teams had previously emerged triumphant in the 15-year history of the tournament, Munster not only stormed the Perpignan citadel, but came away with a precious bonus point for scoring four tries into the bargain.
Written off almost everywhere following last week's limp 24-23 result over the same opposition in Limerick, Munster's underwhelming form made it seem that the journey to the south-west of France would probably mark their exit from the cup.
But with their traditional ferocity coursing through every player once again, they out-muscled and out-thought Perpignan with a display for the ages. Denis Fogarty, Denis Hurley, Jean de Villiers and finally Doug Howlett scored the tries with Ronan O'Gara adding 17 composed points from three penalties and four conversions.
With Perpignan now eliminated, the pool has come down to a two-horse race between Munster and English club, Northampton, and if Munster win in Italy against Treviso and then defeat Northampton at Thomond Park in next month's series of matches, they are almost certain to secure a home quarter-final.
"It has to be one of the greatest away wins in Munster's history," said coach, Tony McGahan, who had been coming under increasing pressure for the unconvincing way his team was performing. "You always believe you can go away and achieve any result with this group of players. You don't underestimate their belief, character, and pride in the Munster jersey - you don't doubt that at any point. The result has given us a lot of confidence, but we need to march on from here and view this as a starting point."
For captain, Paul O'Connell, who turned in a barnstorming individual display, the win came as a "big step forward" for the players. "Sometimes your confidence can go, and different things start happening and you start over analysing yourself. Sometimes the harder you try the worse you can get, and I think that happened a little bit with us. When we play with intensity, I think we're a very good side. We weren't ever trying to be anything other than the real Munster."
In front 10-9 at the changeover, Munster pressed on with real conviction in the second half as Hurley, then De Villiers with a brilliant solo effort and Howlett put Perpignan to the sword.
Even though they won in the end last week, Leinster came home from Wales disappointed that they had failed to really put the Scarlets away. Well, they made up for whatever frustration lingered by finishing the job with a ruthless 39-7 performance at the RDS.
Admittedly, the Scarlets looked about as sure of themselves as men walking to the gallows by the time Leinster had wrapped up the bonus point early in the second half, but this was still an utterly professional display by the champions. Seven tries scored, one conceded, and it didn't even matter that replacement out-half, Shaun Berne, struggled with his placekicking in the swirling breeze.
Strange to think that this time last year, Leinster were in the horrors. Stung by a torrent of negative criticism and seemingly on the verge of an embarrassing exit from Europe, not too many people outside the inner circle could have predicted the good times coming down the line.
London Irish's bonus-point win over Brive surely now means that the rematch at the Madjeski Stadium in the final series of games next month will be a mouth-watering winner-take-all affair, however, it's also possible that both Leinster and London Irish could make it through to the quarter-finals.
The only negative in an ultra-confident effort was a first-half injury to prop, CJ van der Linde. Although the South African World Cup-winner missed a large part of last season due to a toe problem which required surgery during the summer, coach Michael Cheika confirmed that Van der Linde had only suffered a calf strain.
Overall, Cheika was pleased with his side's performance. "It was a bit easier than I thought it would be because they're a pretty dangerous team when they get their stuff going, and we made some elementary errors early on and gave them some opportunities and we were they weren't able to take them. Then we got our shape back and then took the chances that came our way. There was a section of the game when we took our mind off it. We did it last week too. I don't want to be too hard on the players, but it is something we need to eradicate."
Leinster led 15-0 at the interval and they secured the bonus with the first of Gordon D'Arcy's two tries just after the break. Brian O'Driscoll and Rob Kearney also crossed for two apiece, while the impressive Shane Horgan also got in the act with an interception and a 70-meter run.
Although the tricky wind made conditions difficult for placekicking, Berne's return of two from eight was a disappointment. Jonathan Sexton's broken hand is being assessed, and while Ireland's new out-half might not be available for the Ulster game on St Stephen's Day, it looks certain that he will make his return against Connacht the following weekend.
Meanwhile, for Ulster there was the disappointment of having their game against Stade Francais in Brussels postponed due to an icy pitch on the Saturday, and then losing 29-16 when the fixture was moved to Paris on the Sunday.
With the Stade scrum-half, Julien Dupuy, banned for six months after being found guilty of eye gouging Stephen Ferris in the first game in Belfast, the French played with more focus and less ill-discipline this time.
Dominant virtually throughout, Ulster were trailing 29-9 when Andrew Trimble burst through for a fine individual try with 10 minutes left, but there was little prospect of another score and a losing bonus point.
Now trailing Stade in the pool by four points, Ulster are still mathematically in with a chance of qualifying for the knockout stages, but they will need to win their two remaining matches against Edinburgh and Bath, and hope that the French slip up.
If Connacht's form in the Celtic League has been nothing to shout about - just two wins all season and still at the bottom of the table - they have been faring infinitely better in Europe's Challenge Cup and last week's convincing 19-7 victory over Worcester in Galway keeps them right on track for the knockout stages.
Although their English opponents took a surprise early lead, Connacht soon hit back with tries by John Muldoon and Gavin Duffy as well as two penalties and a drop goal from Ian Keatley. Now two points clear at the top of their pool, if the Westerners manage to defeat Montpellier at home and Madrid away, they will be certain of a place in the last eight.