Right from the off Saints showed that they were in the mood to take advantage of the clear summer afternoon, George Pisi and Dom Waldouck combining superbly down the left wing with the former only being denied a try when a Ryan Lamb chip bounced away from the Samoan. The forwards were warming to their task, too, setting up a powerful maul from their first attacking lineout.
But while there was plenty of pressure, scoring opportunities were hard to come by in the opening quarter. A Paul Diggin pass to Waldouck evaded the centre to float into touch, and Leinster held firm at a five-metre scrum.
It was only temporary respite, however, as Noel Reid's kicking from hand played straight into Saints' hands. A wayward touchfinder set up a Vasily Artemyev attack, and although the visitors held out the initial run back their defence proved powerless to stop Waldouck. The centre looked to have run up a blind alley, but his legs kept pumping and eventually Waldouck worked his way through the tacklers, into the clear, and over for his first Franklin's Gardens try.
The second try came six minutes later and it was a peach. Saints again opted to turn a penalty into a scrum, but once the ball was secured the backs were set loose. This time everything went to plan, the dummy runners held the defenders and some sleight of hand from Dickson and Lamb, and good timing from Foden, put Diggin over in the right corner.
The crowd in the Shrubbery Terrace were treated to another good score eight minutes after that. Like its predecessor, this try was created by some great handling, this time Phil Dowson. His slipped ball out of contact put Foden into the clear, Artemyev the recipient of the final scoring pass.
Leading 17-0 at the break, Saints found themselves a man down two minutes after the re-start when Luther Burrell's over-exuberance in the tackle earned the replacement centre a yellow card.
Leinster used this as the impetus for their most dangerous attack of the game thus far. But while Boss found his way over the line he did not count on Lee Dickson, who pulled off a superb tackle to hold the Irish scrum-half off the ground.
This effort galvanised the rest of the defence, and the pressure from the Saints won a turnover and nullify the danger.
Saints were still down to 14 men, but they belied the disadvantage by coming within a metre of extending their lead. In the first half Ken Pisi had showed his twinkling toes; in the second 40 his pace, power and handling skills came to the fore, and were so nearly rewarded when Tom May put him into space, only for the defence to scramble and force the Samoan into touch.
Saints continued to press, but while there was plenty of action as a raft of replacements bedded themselves into the pace of the game scoring opportunities were hard to come by.
Tom Wood came closest in a charge to the line, and while the England flanker was to find himself on the end of the game's fifth try it was its predecessor three minutes earlier which raised the roof.
The full back may have changed - James Wilson having replaced Foden at half-time - but the skills were just the same, the Kiwi slipping a great pass to Scott Armstrong for the score. And Ben Nutley showed similar prowess in Saints' sixth, grabbing the ball off his bootlaces to keep a move alive which ended in a try for Tom May.
Noah Cato's awareness had put May clear, and the centre returned the favour two minutes later. Cato sped over, Myler added the extras once again, and Saints fans headed home happy.
23mins SAINTS Try Waldouck 5-0
29mins SAINTS Try Diggin 10-0
37mins SAINTS Try Artemyev Con Lamb 17-0
HALF-TIME SAINTS 17 LEINSTER 0
41mins SAINTS Yellow card Burrell
68mins SAINTS Try Armstrong Con Myler 24-0
71mins SAINTS Try Wood Con Myler 31-0
79mins SAINTS Try May 36-0
81mins SAINTS Try Cato Con Myler 43-0
FULL-TIME SAINTS 43 LEINSTER 0