The second half felt a different game. Less than a minute after the restart, Leinster had their fourth try of the contest.
Robbie Henshaw and Jimmy O’Brien linked up well in the passage preceding South African lock Jason Jenkins going over, and the try was to represent the opening of the floodgates.
Henshaw was centrally involved again for Leinster’s fifth try with his carry and pass sending Larmour over in the corner for a second, after Dan Edwards had fumbled forward when attempting a kick.
With the strength of Leinster’s bench apparent, Leo Cullen’s men would add gloss to the score with four tries across the game’s final 11 minutes.
Tommy O’Brien was one of the impressive replacements for the home side and it was his charge forward that created a try for Jamie Osborne.
A well-worked move off the line-out left the space for another replacement, Charlie Ngatai, to get in on the act, before Larmour completed his hat-trick with four minutes remaining.
Having created one score, Tommy O’Brien claimed one of his own in the last minute to round off another big win for Leinster.
Leinster: Frawley, Larmour, Osborne, Henshaw, J O’Brien, Byrne, McGrath; Porter, Kelleher, Furlong; Molony, Jenkins; Baird, Van der Flier, Doris (capt).
Replacements: Sheehan, Milne, Clarkson, Conan, Penny, Gibson-Park, Ngatai, T O’Brien.
Sin-bin: Frawley (18)
Ospreys: Nagy; L Morgan, Watkin, Williams, Giles; Edwards, Morgan-Williams; Smith Lake, Henry; Ratti, Sutton; Deaves, Tipuric (capt), Morris.
Replacements: Parry, Thomas, Botha, Sekekete, J Morgan, Davies, Walsh, Boshoff.
Sin-bin: Boshoff (76)
Referee: Sam Grove-White.