The visitors were roared on by 3,000 travelling fans as they sought to make club history and progress into the last four, and they made an excellent start to be 10-0 up after quarter of an hour.

James - in a telling foretaste of his later struggles - missed an early penalty, but it was the Aussie fly-half's delicate chip that enabled Aurélien Rougerie to tee up Malzieu for his opening score after just 12 minutes. James added the conversion and a subsequent penalty to give the travelling hordes plenty to cheer, but it was merely the first installment in a see-saw battle that had fortunes swinging more wildly than a drunken golfer.

Jonny Sexton - who kicked seven out of eight attempts on the night - began the Leinster fightback with a regulation penalty, before a trademark Brian O'Driscoll jink paved the way for Ireland number eight Jamie Heaslip to storm over in the 24th minute. Sexton's conversion made it all square before James skewed two kickable penalties in reply as Clermont's early dominance filtered away.

Leinster then claimed the lead for the first time in the match when Heaslip powered over for his second try on 34 minutes, and with Sexton adding the extras and another penalty the French side somehow went in half-time trailing by 10 points as Leinster lead 20-10. Morgan Parra's long-range effort also sailed wide before the interval to rub further salt in Clermont's opening wounds.

But Vern Cotter's team have built a deserved reputation for flowing rugby in recent years and the Michelin-backed outfit ran in a splendid second try just four minutes after the restart when Malzieu finished off another fluent attack.

James was unable to convert this time, but had more luck with two subsequent penalties - in reply to another from Sexton - before Malzieu completed his hat-trick of tries on the hour mark after charging down Shane Horgan's attempted clearance. James' conversion made it 23-28 to Clermont and seemingly set up the French for a memorable victory at the RDS, but the match still had a final twist or two to play out.

Two further Sexton penalties edged the home side back ahead by the 73rd minute but Clermont still had chances to claim the victory only for James to prove wayward again with two late drop-goal attempts.

It was cruel on the visitors - and especially on Malzieu - but in the end they only had themselves to blame after squandering a massive 23 points in missed kicks.

So, there will be no all-French semi-final after Clermont wasted the chance to meet the winners of Stade Toulousain and Stade Francais, with that honour now going to the defending champions after they rode their luck in front of a passionate but at times disbelieving crowd.

Leinster: 15 Rob Kearney, 14 Shane Horgan, 13 Brian O'Driscoll, 12 Gordon D'Arcy, 11 Isa Nacewa, 10 Jonathan Sexton, 9 Eoin Reddan, 8 Jamie Heaslip, 7 Shane Jennings, 6 Kevin McLaughlin, 5 Nathan Hines, 4 Leo Cullen (capt), 3 CJ van der Linde, 2 John Fogarty, 1 Stan Wright.
Replacements: 16 Bernard Jackman, 17 Mike Ross, 18 Cian Healy, 19 Malcolm O'Kelly, 20 Stephen Keogh, 21 Paul O'Donohoe, 22 Shaun Berne, 23 Girvan Dempsey.
Tries: Heaslip (2)
Convs: Sexton (2)
Pens: Sexton (5)