When Jacques Brunel, the Italy-bound coach of Perpignan, predicted in the build-up to this Heineken Cup semi-final that the occasion would have a "perfume" all of its own, those Northampton followers fearing that the myths and legends surrounding the Catalans' forward strength might turn out to be true assumed the smell in Brunel's nostrils was one of purest sulphur.
Actually, it was one of stereotype. The visitors' performance yesterday could not have been more hackneyed if it had been scripted by the UKIP leader Nigel Farage.
They fell out with the Irish referee, George Clancy, early in the piece; they lost their focus, their discipline and their collective temper at one and the same time; and when they failed to start a decent argument with their opponents, they argued among themselves instead.
This was French rugby, UKIP-style. There was barely a cliché they did not fulfil, short of cycling on to the field with strings of onions on their handlebars.
For long periods, Northampton were not so much the better side as the only side. Perry Freshwater, the occasional England front-rower who has been playing his rugby on the Franco-Spanish border for the best part of a decade and started this contest at loose-head prop, was honest enough at the final whistle. "I don't know whether that's the best pack of forwards around, but credit to them: they were smart and they were very intense. I don't mind admitting that I found it hard going out there."
Hard going? He could say that again, and probably did. Freshwater was not the only Perpignan big-shot to find himself firing blanks as the Midlanders took charge of the scrums, the rucks, the edges, the midfield tackle zone and just about everything else.
Nicolas Mas, considered by some to be the best tight-head prop in the game, spent most of the afternoon in retreat, and when he left the field three minutes from time, he looked atomised. Guilhem Guirado, the brilliant young hooker, was a lot less brilliant than his opposite number, Dylan Hartley, while Damien Chouly, a hot tip for the French World Cup squad, was barely visible.
Only Bertrand Guiry, the wild-eyed bandit in the back row, and Robins Tchale-Watchou, the huge West African lock, showed anything at all in what rugby players politely describe as the "shit-fight".
What naked aggression the Catalans offered was largely to be found outside the scrum. David Mele, the scrum-half, was in a fearful strop for much of the first half, and when Julien Candelon took out the Northampton half-back Lee Dickson in mid-air from a restart, he might easily have had a red card flourished in his direction. Instead, Clancy took the tolerant approach and settled for yellow. Perhaps he knew, half an hour in, that the outcome was beyond dispute.
The miscreant on the left wing had a rough old day, one way or another. Before his sin-binning, he committed the butter-fingered error that presented Northampton with the position from which they scored their second, game-breaking try. After his return from the cooler, he conceded the penalty that yielded the only points of a flat second half. If you really wanted to rub it in, you might say Candelon got on Clancy's wick.
At no point did Northampton need help from the officials to reach their second Heineken Cup final, 11 years after winning the trophy through the efforts of Paul Grayson and Garry Pagel, Budge Pountney and Pat Lam. They received plenty, all the same.
The Saints were nicely in control after a smart finish from Ben Foden on 14 minutes and a penalty from Stephen Myler on 24 minutes when the goal-kicker's opposite number, Nicolas Laharrague, chipped dangerously for David Marty behind the defensive line.
The move had "try" written all over it, but the referee decided at least one Perpignan back had mistimed his rush and fallen offside. He was wrong, and the furious Frenchmen knew it. What could they do about it? Nada.
From that point on, leaving aside Guirado's mauling try at the end of the first half, Northampton had it all their own way. When Tchale-Watchou, hardly the least visible man on the field, was penalised for slipping in the side of a ruck – Brunel did not agree with this decision, either – Myler had a long kick for a 13-point lead. He sliced it horribly, and the ball drifted towards Candelon, stationed near the corner flag. Embarrassingly, the wing fumbled his gather under pressure from the pumped-up Phil Dowson, and from the subsequent scrum and line-out, Jon Clarke waltzed through some kindergarten tackling to touch down at the sticks.
If Clarke ever scores an easier try at this exalted level of rugby – highly unlikely, it has to be said – it will not be against the Leinster centres Brian O'Driscoll and Gordon D'Arcy in the final at the Millennium Stadium on Saturday week.
Jim Mallinder, the Northampton rugby director, hinted at this during the post-match discussion when he said: "Leinster have world-class players running through their side, players who are used to playing big-occasion matches and are used to winning trophies."
It was a comment that underpinned Hartley's public assumption of underdog status, yet Mallinder was in no sense down-playing his side's chances. "We've been criticised a little bit for being one-dimensional," he said, "but I think we played an all-round game out there. Anyway, the fundamentals don't change. You win rugby matches with a top-notch pack of forwards, a mix of power and creativity in midfield, finishers in the back three and a strong defence. We think we can bring those things to the final."
Or as the increasingly impressive Hartley put it, a little more succinctly: "When we turn up with the right mindset, we can beat anyone."
Leinster will indeed start as favourites, but this 16th Heineken Cup tournament is far from a done deal. Since the change to a home-and-away pool format in the 1997-98 season, no team has reached the final unbeaten. Until now. And we're not talking about the Dubliners.
Scorers: Northampton: Tries: Foden, Clarke. Conversions: Myler 2. Penalties: Myler 3. Perpignan: Try: Guirado. Conversion: Porical.
Northampton: B Foden; C Ashton, J Clarke (J Ansbro, 81), J Downey, P Diggin; S Myler, L Dickson (S Commins, 83); S Tonga'uiha (A Waller, 83), D Hartley (capt, B Sharman, 83), B Mujati (T Mercey, 81), C Lawes, C Day (M Sorenson, 77), C Clark (M Easter, 83) P Dowson, R Wilson.
Perpignan: J Porical (J Michel, 72); A Plante, D Marty, G Hume, J Candelon; N Laharrague (M Edmonds, 75), D Mele (K Boulogne, 75); P Freshwater (J Schuster, 61), G Guirado (C Geli, 77), N Mas (capt, K Pulu, 77), R Alvarez Kairelis (G Vilaceca, 70), R Tchale-Watchou, G Le Corvec (H Tuilagi, 50), B Guiry, D Chouly.
Referee: G Clancy (Ireland).