Dubbed 'The Last Stand', this provincial derby marked the end of an era as little over 130 years after these sides played out the first ever rugby fixture at the famous Dublin stadium, they brought the curtain down on Lansdowne Road as it currently exists.
February will see the wrecking ball move in and a new 50,000-seater stadium is projected to be ready in time for the 2009 autumn internationals.
Just as they did on December 16, 1876, Leinster managed to beat the visitors and in front of a record Celtic League crowd of 48,000. The wind and rain failed to spoil a carnival day for Irish rugby, which even included a half-time marriage proposal.
Disappointingly David Humphreys, who captained Ulster to Heineken Cup glory at the Dublin 4 venue in 1999, had his afternoon cut short by a fifth-minute shoulder injury.
Leinster took their cue from there with Gordon D'Arcy probing and pressing at every opportunity. Malcolm O'Kelly showed well at lineout time and in the loose, but Ulster, with the wind advantage, edged the first half 12-5.
Former Ulster prop Ronan McCormack was caught offside at a 22nd-minute ruck and Humphreys' replacement Wallace speared over the penalty for the game's first points.
Frustratingly for Leinster coach Michael Cheika, the penalty count against his side grew as the half went on and Wallace obliged again with a difficult 33rd-minute penalty kick, drawing it in from the left.
A quick tap penalty from Isaac Boss then set Ulster on the attack and hands in the ruck from Will Green saw Wallace, with the aid of the upright, notch a superb third penalty from the right flank.
Leinster roared right back, winning the restart and man of the match Stephen Keogh was unfortunate not to cross in the right corner after a great build-up from Brian O'Driscoll and Shane Horgan. The former Munster back rower lost control of the ball over the try line as Andrew Trimble put in a hefty challenge.
However Cheika's men regrouped and Horgan popped up on the left wing to put Denis Hickie over from close range for his fifth try in 10 league games, taking the Ireland winger's league record to 27.
Jonathan Sexton's conversion attempt bounced back off the post and Ulster managed to have the last word of the first half with a wonderful drop goal from the on-fire Wallace.
It was effectively a tale of two halves as Leinster succeeded in dominating the second half, with the aid of the elements. Young number 10 Sexton struck a penalty, six minutes in, and was unfortunate to miss another place kick just moments later.
Despite losing Hickie, who was yellow carded for killing the ball as Ulster pressed for a try with numbers out to the right, Leinster picked up their second try while down to 14 men.
Replacement lock Finegan, who clashed with his former Wallaby team mate Justin Harrison in the aftermath of his score, crashed through Paul Steinmetz's tackle on 64 minutes after a barrage of Leinster attacks.
Felipe Contepomi, showing no ill effects of his recent knee injury, converted and the Pumas star showed lovely hands in the build-up to Heaslip's 77th-minute effort.
Ulster, for whom Wallace missed a penalty on the hour, were completely stretched as snipes from O'Driscoll and Kieran Lewis and a timely offload from Bernard Jackman put Heaslip over in the right corner, signalling some early New Year's celebrations for Leinster's fifth win in their last six meetings with their northern counterparts.