This game was billed as a "Christmas Cracker in the Aviva" but in the end it proved to be a bit of an old turkey as Leinster managed to come out on the plus side of a bruising scrap.
The faces on the home supporters told a Christmas tale of their own, relieved at the one-point win but again frustrated with this Leinster team and the way they are playing the game.
Once again, coach Matt O Connor will say what he has every right to say - that the most important thing is winning - and to an extent he is right. But winning ugly every week is starting to gnaw a little.
Over a two-week period, what have we learnt? Only that these two teams are exactly where they started, apart from a try differential in the head to head games that won't favour Leinster should the two teams still remain chained at the hip in a few months time.
One thing seemed pretty certain to most onlookers - unless both teams improve exponentially over the Christmas period then we are not seeing the eventual winners of this competition from this pool.
It was a hard game to watch, often punctuated by long periods with the video referee when old fashioned refereeing laws would have said "just get on with it," especially in the last few minutes when a handbag scuffle from both teams saw the crowd waiting for nearly six minutes before Harlequins second-row Charlie Matthews was eventually found to be the most guilty of a few culprits.
A few years ago I was talking to the All Black management team. At that time they were concerned about the physical size of players that England and South Africa were now able to field and they knew that to compete they would have to change the way they played. And so they did.
The All Blacks went back to basics and concentrated on skill, appreciation of space and tempo. Players like the magnificent No 8 Kieran Read emerged, players not all about brawn but more about brain.
The All Blacks figured that if they could retain ball for long periods and move the bigger packs around the track at speed, then they could continue to dominate the world game. For the most part the philosophy is still working pretty well.
Likewise, when Joe Schmidt arrived in Dublin he reinvigorated the likes of Brian O'Driscoll, Shane Horgan and Denis Hickie by promising them at his very first training session that he would "make them the best passing team in Europe".
The long way around to my point is this - last night we witnessed what rugby anoraks will describe as a "bruising encounter" and while that is true, it was also a game that hardly saw a clean line break all evening, and a game where the kicking out of hand from both sides was too often just for the sake of it rather than planned kicks for reward.
We saw plenty of strong-arm carries from the likes of Leinster's hooker Sean Cronin and flanker Dominic Ryan, but just when you wished a player would offload or see a player in a better position, they died with the ball. There was no appreciation of where the space on the field was.
The result a defence-dominated game with the ball and momentum too often slowed to a dribble.
As a contest, last night's game could have gone either way. As I took my seat for the second half, a big Leinster mitt was thrust into mine.
"Bet ya we win by five tries," the blue scarf-wearing gentleman confidently boasted. I had to agree. Leinster had not played well in the first spell but they led by at least two clear scores and would surely kick on.
But it was the visitors who upped the tempo, despite having a young out half clearly out of his depth but not really tested by Leinster, often requiring a reassuring pat on the head by his team-mates every time he messed up.
Harlequins' excellent fullback, Mike Brown, looked to have done enough when he latched onto a clever kick from his lively scrumhalf, Danny Care, but the video ref had to go back three phases to presume that a Harlequins captain Joe Marler had knocked the ball on.
It was hard to say whether that was the case or if a Leinster hand had stripped the ball back illegally, but Leinster survived, momentarily.
Brown was soon over for a second bite and this time the try stood. Harlequins suddenly had the bit between their teeth and actually turned an 11-point deficit into a two-point lead turning into the final straight.
Games as tight as this hinge turn on small margins and a clever dummy and break by replacement scrumhalf Eoin Reddan as the point at which they actually won this game.
It was then and only then that Leinster significantly upped their intensity, knowing that at least they were not camped in their own 22.
Ian Madigan's 72nd- minute penalty sealed it but not before Leinster let Harlequins have one more shot at a win before they too messed up.
Overall summation? Leinster's scrum again faltered badly, something that will concern the national coach, as will Leinster's lack of any real creativity in the midfield. Ian Madigan played well enough in patches but still looks a bit light for a number 12, while outside him Luke Fitzgerald again impressed with good footwork and aggression.
In the engine room, Sean Cronin was Leinster's main go-to man, followed by Dominic Ryan, Jamie Heaslip and Jack McGrath.
O'Connor will continue to get key players back and qualification is still very much in Leinster's hands.