Saints refused to suffer another Leinster fightback as George North’s double helped secure a 33-21 pre-season victory at Franklin’s Gardens.
There were echoes of the 2011 Heineken Cup final when the Irish giants hauled themselves back to just five points behind having been 26-0 down, but North had the final say to secure the win.
The Wales wing picked up a Cam Dolan pass and stormed in for a fine score that put the finishing touches on a success Saints were eventually made to work hard for.
They had been cruising at the break as Samoan scrum-half Kahn Fotuali’i lit up the Gardens with an impressive solo peformance.
He latched on to a neat Will Hooley pass to add to Tom Stephenson’s early score, before setting up a try for Luther Burrell with a clever break and offload.
North made an immediate impact after the break with Saints looking likely to rack up a huge total.
But Leinster stuck at it and Cian Kelleher, Dan Leavy and Mick McGrath made it a little nervy before North struck to seal the success.
Leinster had enjoyed the better of the early exchanges, but a poor set piece, particularly the lineout, let them down.
Instead, it was Saints who opened as England Under 20s centre Stephenson burst through the visiting defence to score.
Fly-half Hooley added the extras, but there was disappointment for Stephenson as he was forced off, holding his left arm.
Phil Dowson also left the field soon after, thrusting trialist Jon Fisher into the action and Saints continued on the front foot.
Leinster just could not get their lineouts right and after another went into home hands, Ben Foden knocked on with the line in sight.
Fotuali’i was starting to come to the fore, with his fielding of the high ball and quickening of the tempo pushing Saints forward.
And it wasn’t long before the razor sharp Samoan No.9 had a try to his name, flying onto a neat inside pass from Hooley and skidding over the line.
Hooley made it 14-0 with the simple conversion and Leinster were soon down to 14 men as lock Ben Marshall was sent to the sin bin.
It was all Saints and all Fotuali’i, who was pulling the strings, scything through Leinster again before offloading to England’s Burrell for another fine score.
The 21-point lead didn’t flatter the home side and Leinster were struggling to cope with the intensity levels of the Premiership champions.
Both sides made a raft of changes at the break and one of the Saints replacements, North, cruised over unopposed on the left.
Hooley missed the tricky conversion and Leinster were soon over for their first score of the day, full-back Kelleher making the most of good work from Cathal Marsh to score.
Marsh added the extras and Saints were on the back foot, losing Lee Dickson to a sin-binning for what was deemed a dangerous tackle on Steve Crosbie.
Leinster profited as flanker Leavy scored his team’s second try, with Marsh cutting the gap to 12 points with the conversion.
And Saints were soon sweating over the win as McGrath went over to bring his team within touching distance of the lead.
North was not prepared to let it lie, though, dodging the final defensive obstacle and dotting down.
James Wilson put the gloss on proceedings with the conversion.
Saints: Foden (Wilson 57); Elliott (K Pisi 57), Waldouck, Stephenson (Burrell 14), K Pisi; Hooley (Olver 65), Fotuali’i (L Dickson 40); Corbisiero (A Waller 40), McMillan (Hartley 40), Ma’afu (Denman 40); Craig, C Day (Dolan 40); Dowson (Fisher 15), Wood (c) (Clark 40), Manoa (Lawes 52).
Leinster: Dardis (Kelleher 50); Fanning (A Byrne 57), Macken (O’Loughlin 57), Coughlan (Crosbie 50), Coglan-Murray (M McGrath 50), Gopperth (c) (Marsh 40), Boss (L McGrath 40); Bent (S McCarthy 32) (E Byrne 68), B Byrne (Moran 62), Furlong; Marshall (Thornbury 40), Denton; van der Flier, Leavy, Ryan (Slattery 62).
Referee: Luke Pearce