James Lowe scored a hat-trick of tries as Leinster survived a late scare to beat Northampton 20-17 at Dublin's Croke Park on Saturday to reach a third successive Champions Cup final.
The Ireland wing crossed twice in four minutes early in the first half in what was effectively a home semi-final for Leinster, who are based across town at Donnybrook.
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Leinster will now look to go one better after losing the last two Champions Cup finals to a La Rochelle side coached by Ireland great Ronan O'Gara when they face the winners of Sunday's semi-final between record five-time European kings Toulouse and Harlequins at London's Tottenham Hotspur Stadium on May 25.
Four-time European champions Leinster dominated the opening 40 minutes to lead 15-3 at the break.
And when New Zealand-born Lowe, 31, went over early in the second half, the Irish province were in command at 20-3.
But with Leinster fly-half Ross Byrne repeatedly off target from the kicking tee, Northampton recovered and when replacement Tom Seabrook scored a converted try six minutes from time, they were just three points behind.
Leinster captain Caelan Doris, however, sealed victory when the Ireland No 8 won a key turnover penalty at a breakdown with a minute left.
"We were able to build a score and then we know Northampton are an amazing attacking side," Lowe told TNT Sports.
"We gave them too many opportunities and we didn't kick well."
Lowe said his try treble owed much to the work of Ireland scrum-half Jamison Gibson-Park, with the wing insisting only France's Antoine Dupont rivalled him in the position among current players.
"I ran 10 metres in total for all three of them," he said. "There is a reason why Jamison is the best nine (scrum-half) in the world...He sees space no one else sees."
Northampton were without injured captain Lewis Ludlam and wing Ollie Sleightholme, sidelined following a concussion. Former England skipper Courtney Lawes led Northampton in Ludlam's absence.
Leinster's early dominance was rewarded when they opened the scoring in the 10th minute. Gibson-Park's quick tap penalty near the Saints' line caught Northampton napping and his superb long pass allowed fellow Ireland international Lowe to score at the left corner.
Four minutes later, Lowe had a second try. Byrne made a break and Leinster's pack then took up the charge with a rolling maul that collapsed in sight of the try-line. But Gibson-Park knocked the ball back to Lowe for another try in the corner.
This time Byrne's conversion hit the left post but Leinster were 12-0 ahead to the delight of a crowd of over 82,000.
Leinster were then awarded a scrum penalty, Byrne making no mistake from close range to extend his side's lead to 15-0 on the half-hour mark.
Northampton's first sustained handling move ended with James Ramm knocking on from a pass behind him when a try loomed but play was brought back for a penalty, with Fin Smith on target as the Saints at last got on the scoreboard.
Lowe, however, completed his hat-trick just three minutes into the second half after a surging run by blindside flanker Ryan Baird.
Northampton hit back with their first try of the game when Leinster failed to deal with George Hendy's chip over the defence before the wing regathered to score in the corner.
Smith converted and Northampton had a glimmer of hope at 10-20 behind heading into the final quarter, with Byrne missing a 40-metre penalty that would have put the result beyond doubt.
Byrne's errors were compounded when Northampton replacement Seabrook crossed in the 74th minute after the Saints punched holes in Leinster's defence, with Smith's conversion setting up a thrilling finish.
