Superb for 50 minutes or so, and almost supine for the last half an hour, this one followed the trajectory of their previous two outings away to Glasgow and Edinburgh even if there was never a point when defeat threatened.
Leinster had opened their seasonal account with a visit to Dublin by Treviso before spending those two weekends in Scotland so this was the first real sense of occasion to hit the RDS since last May’s semi-final defeat of Ulster in Ballsbridge.
It delivered. Sexton’s return to the starting line-up only heightened that feeling and the feel good vibes reverberated through a first-half dominated by the home side who found the break with 24 points scored and none conceded.
The positives were obvious.
Sexton put in a perfectly good shift until a late yellow card dirtied his bib and a committed collective was spearheaded by the bullocking Josh van der Flier up front and the dogged Dave Kearney out the back.
Ospreys played some decent rugby in spurts and could have answered the hosts’ opening penalty and first try with a five-pointer of their own had Jeff Hassler not butchered an overlap and allowed Isa Nacewa to nail him 23 minutes in.
A few other aborted invasions of the Leinster 22 aside and it was all traffic in the opposite direction with Ospreys conceding 10 penalties in the first-half and losing prop Dmitri Arhip to a yellow after 27 minutes.
Arhip walked as punishment for his team’s repeated infringements rather than the seriousness of his act in clothes-lining Nacewa but a worse call followed within minutes when the TMO ruled out a try for Luke McGrath.
Replays clearly showed Sexton dropping the ball behind him as a bunch of Ospreys pulled him over the touch line but ‘knock on’ was the belated ruling much to the astonishment of the crowd.
Another dodgy officiating in the PRO12 then, though it was a rare sour note.
Van der Flier had already claimed the first try at the start of the second quarter, trundling over after six close-in phases, and Arhip’s exit destabilised the Ospreys scrum enough for Leinster to claim a penalty try seven minutes from the interval.
Neither a thing of beauty then but it had been brutally effective and Leo Cullen’s men combined grace and graft in breaking from midfield on the stroke of half-time and setting up Sexton to go over for a satisfying third.
It made for a comfortable cushion, even for a side that had struggled with those commanding advantages the last fortnight, and Leinster stretched it within six minutes through van der Flier’s second converted try.
Bonus point secured, there was an inevitability to the next chapter with Ospreys finally enjoying a spell of possession and one that should have delivered a try only for Rhys Webb, of all people, to drop the ball when through on the posts.
Leinster paid little heed to the warning.
Ben John dotted down four minutes later after the home defence was sucked into a succession of forward drives and then Dafydd Howells and James King followed him in in the last 10 minutes.
That was that, though.
Terrific fun. Again.
Z Kirchner; I Nacewa, G Ringrose, N Reid, D Kearney; J Sexton, L McGrath; C Healy, S Cronin, T Furlong; D Toner, M Kearney; J Murphy, J van der Flier, J Heaslip.
J McGrath for Healy and R Ruddock for Murphy (both 50); R Molony for M Kearney and J Tracy for Cronin (both 55); J Gibson-Park for L McGrath (61); M Ross for Furlong (65); J Carbery for van der Flier (72); D Leavy for Sexton (80).
S Davies; J Hassler, A Beck, J Matavesi, B John; D Biggar, R Webb; P James, S Baldwin, D Arhip; L Ashley, AW Jones; J King, J Tipuric, T Ardron.
M Fia for King (30-40); D Baker for Ardron, N Smith for James and S Parry for Baldwin (all 48); B Davies for Ashley (50); D Howells for Hassler and T Habberfield for Webb (both 61); M Fia for Arhip and D Evans for Beck (both 66).
M Mitrea (FIR).