Because after the world famous DJ had smashed an ice sculpture to reveal the match ball - in a ceremony that surely proves the Gallagher Premiership is the most glitzy league of them all - Chris Boyd’s side had danced into a 21-7 lead.
But what unfolded after that ensured this was a night to forget rather than one to remember.
Rather than kicking on and bagging a bonus-point win, Saints were eventually left with absolutely nothing to show for their efforts.
Harlequins roared back to lead 26-24 at half-time and then piled on the pain late on, scoring two second-half tries that made sure Saints would not even take the consolation of a losing bonus point back to Northampton.
It was agonising for everyone of a Saints persuasion after such a dazzling first 15 minutes during which Juarno Augustus powered over twice and Alex Waller scored on the hallowed turf again.
Saints were cutting Quins apart but if you can’t keep the door closed at the other end of the pitch, you are always going to be in trouble against a side who have shown they can score tries for fun.
And so it proved.
Quins, so adept at comebacks, refused to be deterred by the concession of three early tries and their attacking accuracy in the red zone helped them get a foothold in a frenetic game.
Then when it came to Saints having to chase the game in the second half, familiar demons resurfaced as they seemed to lose their ability to hold on to the ball.
Time and again, they knocked on in the Quins half.
And time and again, they were penalised by referee Wayne Barnes.
Eventually, the misery was complete as Courtnall Skosan kicked the ball dead and Quins set up a scrum from which former Saints target Alex Dombrandt completed his hat-trick.
It was a day to savour for the No.8 and the champions - just as it was when Samu Manoa helped then Premiership holders Saints to beat Quins at Twickenham exactly seven years earlier.
This game was actually a microcosm of what has happened since to Saints that December day in 2014.
They have often promised plenty but delivered so little during that seven-year period.
Just when you think they are rising again, they fall.
It is painful for everyone connected with the club that they seem to get to a certain point and good things slip away.
This Saints team, having been third before the weekend began, are now down to fifth.
And if they are not careful, the top-four race could get away from them with the fixture list giving them no reprieve.
They take on Saracens next before a trip to Newcastle Falcons.
And somehow they are going to have to find a way to regain some composure because they know that those teams, as Quins did on Monday, will be ready to pounce if the opportunity presents itself.
How they rated...
Provided some of his trademark cut and thrust as Saints flew out of the blocks, but Quins finally started to stop him having an influence in the second half... 6.5
One clearance and chase summed up his desire but the wing never really got the ball in the kind of positions he wanted and that limited his threat... 6
Really hasn't had much luck with injuries so far this season, and that continued here as he was forced off just after Quins had levelled the scores... 6
Some of his movement in attack was eye-catching and he kept Harlequins on their toes during the first half, but Quins started to get to grips with him... 6.5
Was desperate to carry Saints forward in attack but his game was marred by the late decision to kick the ball away as it went dead and Quins used the final scrum to steal Saints' losing bonus point... 5
Gave away one penalty for sealing off at a ruck but aside from that, the fly-half once again showed why he is so at home on the big stage... 7
Looked razor-sharp at times and his tempo was key as Saints flew into the lead, but Quins started to slow him down as the game went on... 7
Grabbed another try at Twickenham and made 10 tackles without missing one as he showed his desire in defence, but was penalised on a couple of occasions... 6
Got through plenty of work in defence and also helped to keep the Saints lineout secure in a decent overall showing... 6.5
Played his part as Saints moved into the lead but was withdrawn at the break as Saints sought some extra freshness up front... 6
Got on the wrong side of the referee on a few occasions and try as he might he couldn't get the momentum he wanted here... 5.5
Produced one eye-catching offload and was certainly right in the fight as Matt Symons took exception to him and landed a couple of punches that could have been looked at by the TMO... 6.5
Like many of his team-mates he found himself on the wrong side of the referee at times, and Quins were quick to pressure him meaning his ball security wasn't quite there in the second half... 6
Perhaps felt he and Saints were harshly penalised at times, but the flanker doesn't really have a bad game these days, and he was everywhere again... 7
Grabbed a couple of tries to get Saints up and running, and when he was allowed to get his hands on the ball, he always looked a threat... 7.5
Replacements (who played more than 20 minutes)
RORY HUTCHINSON (for Proctor 32)
Showed some flashes of class when he got the chance to attack, especially from deep, but his game ended with a sin-binning... 6
PAUL HILL (for Painter 40)
No shortage of desire but couldn't really make the impact he would have wanted from the bench and was punished by the referee... 5
TOM WOOD (for Augustus 57)
Is certainly no stranger to Twickenham battles and he looked hungry for this one, but Saints were on the back foot when he came on and Quins made life tough as the game went on... 5
CHRON STAR MAN - Alex Dombrandt (Harlequins)