Ulster's fourth Magners League win saw them go top of the table after digging deep to see off current Heineken Cup holders Leinster.
Three penalties and a conversion by Ian Humphreys from a second-half try from Isaac Boss saw Ulster to a 16-14 victory, although a late converted try from the last move of the game from substitute Luke Fitzgerald earned Leinster a valuable bonus point.
Ulster, who were without Paddy Wallace due to the Irish Rugby Football Union's player management programme and Stephen Ferris because of an ankle injury, played the conditions with far more intelligence than their star-studded opponents, who suffered their second league defeat.
With the swirling wind and rain behind them, it was no surprise when Leinster had the opening scoring opportunity after Ian Whitten was penalised for going off his feet at a ruck. However, outside half Shaun Berne was wide with his opening effort from about 40 metres.
The missed penalty certainly set the template for much of the opening half, as neither side managed to get the scoreboard ticking over until a late flurry of points just before the interval.
Berne missed two more penalty attempts before a marvellous forward effort from Ulster - when they retained the ball for around 10 phases - resulted in Leinster hooker Bernard Jackman being sent to the bin after referee Andrew Small blew with the Leinster tryline open for Humphreys and Andrew Trimble.
Humphreys landed the penalty into the teeth of the gale but, from the restart, Leinster turned the screw and, with Brian O'Driscoll pulling the strings, they surged towards Ulster's line in injury time.
Tamaiti Horua was binned for killing the ball, and Leinster ran the penalty with O'Driscoll putting Berne clear for the right corner. The Leinster outside half superbly converted and the visitors trooped off 7-3 in front.
With the conditions now behind Ulster, Humphreys narrowed the deficit with a second penalty five minutes after the resumption and, three minutes later, Boss scooped a ball up from a ruck and broke down the blindside to run in from just short of 50 metres.
Humphreys made the tight angle conversion to give his side the lead 13-7 and was then just short with a penalty attempt from 55 metres.
Leinster were pinned at a scrum on Ulster's line and then saw substitute Jonathan Sexton spill an inside flip pass from O'Driscoll with the Ulster line open.
All that remained was Humphreys' 73rd-minute strike which seemed to take it beyond the visitors, until that is Isa Nacewa's chip through for Fitzgerald, which Sexton converted.
The RBS 6 Nations Championship 2015 was not poised to go down as one of the more "vintage" Championships, though there was great anticipation as the action headed into its final day. What transpired was something that nobody could foresee: "The Greatest Day in Rugby's Greatest Championship."