London Irish 11 Leinster 11:Jonathan Sexton landed an equalising drop-goal with two minutes remaining to knock London Irish out of the Heineken Cup and earn reigning champions Leinster a home quarter-final.
Chris Malone, who had a horror kicking display at Twickenham, looked to have sent the Exiles through as one of the leading two group runners-up when he booted a 77th-minute penalty to put his team 11-8 up.
But seconds after the restart, Ireland fly-half Sexton bisected the posts with a long-range drop as Leinster bagged two crucial points that will see them finish as one of the four highest-scoring group winners.
Isa Nacewa's try had sent Leinster into the break 8-3 up after Malone and Sexton had traded earlier penalties in this Pool Six finale.
Malone got Irish back on terms with a 67th-minute try but he missed the conversion, one of three easy shots at goal he was off target with.
The Londoners came into the match knowing they needed to clinch a bonus-point victory - and also deny Leinster any points - if they were going to finish top of the group, while a defeat would knock them out.
It was a tough ask for Booth's men - and it was clear by half-time that scoring four tries against the holders in their current mood was going to be a mountain too high.
Leinster broke the deadlock through Sexton's fifth-minute penalty from 40 metres and their defence held firm as their opponents battled away in response.
There was a nervousness in Irish's play. Malone shanked wide what should have been a straightforward penalty in the 14th minute and both the Australian outhalf and centre Seilala Mapusua attempted drop-goals that ended up way off target.
Ireland outhalf Sexton was unlucky to see a penalty on the half-hour mark crash against the upright and the ball was snapped up by Exiles winger Topsy Ojo, who embarked on a weaving 40-yard run that ended when he made a forward pass.
Malone found his range five minutes later for 3-3 but Leinster made the ideal riposte before half-time through Nacewa's 38th-minute try.
Moments earlier, the New Zealand-born winger's pass to the lively Gordon D'Arcy, that sent the centre over for a try, was harshly adjudged forward by referee Nigel Owens. But from the resulting scrum, Irish were barged off the ball and ceded possession to Leinster number eight Jamie Heaslip, before Eoin Reddan sent over Nacewa in the left corner.
A 46th-minute dust-up involving Exiles hooker David Paice and Leinster prop Cian Healy saw the latter take 10 minutes in the cooler, but Irish did not take advantage.
Malone missed another routine three-pointer while Mapusua butchered a potential try-scoring chance when he knocked at the end of a decent move that started with a crossfield kick by Malone to Ojo.
Play began to get stretched as Irish got more desperate and with Healy back on, Leinster regained the whip hand. Their midfield pairing of D'Arcy and Brian O'Driscoll carried an ever-present danger, one break from the former nearly setting Shane Horgan away.
Malone's try, then, came somewhat against the run of play. After Mapusua had got over the gainline with a powerful run through the middle, Malone received the ball in the next phase and ignored men outside him to barge over for a 67th-minute score that needed the say-so of the video referee.
Crucially, though, Malone missed the easy conversion, leaving the score tied at 8-8.
It set up a tense finale and Malone turned down the chance of a drop-goal in the 74th minute as an initial opportunity came to nought.
He made amends with two minutes to go with a penalty that looked to have won it for Irish, but Sexton's last-gasp drop saw them knocked out.
Scorers:
London Irish (3) 11
Tries: Malone Pen Malone (2)
Leinster (8) 11
Tries: Nacewa Drop goal: Sexton Pen: Sexton
London Irish:Delon Armitage, Topsy Ojo Elvis Seveali'i, Seilala Mapusua, Sailosi Tagicakibau, Chris Malone, Paul Hodgson, Clarke Dermody, David Paice, Faan Rautenbach, Nick Kennedy, Bob Casey (captain), Richard Thorpe, Steffon Armitage, Chris Hala'Ufia. Replacements: James Buckland, Dan Murphy, Paulica Ion, Gary Johnson, Kieran Roch, Peter Hewat, Peter Richards, Ryan Lamb
Leinster:Rob Kearney, Shane Horgan, Brian O'Driscoll, Gordon D'Arcy, Isa Nacewa, Jonathan Sexton, Eoin Reddan, Cian Healy, Bernard Jackman, CJ van der Linde, Leo Cullen (captain), Nathan Hines, Kevin McLaughlin, Shane Jennings, Jamie Heaslip. Replacements: John Fogarty, Mike Ross, Stan Wright, Malcolm O'Kelly, Sean O'Brien, Paul O'Donohoe, Shaun Berne, Girvan Dempsey
The Heineken Cup quarter-finals qualifiers have been decided with final rankings and quarter-final pairings to be determined after tomorrow (Sunday's) final Round 6 matches in Pools 2 and 5.
The qualifiers in Pool order are:
Pool 1 winners - Munster
Pool 2 winners - Biarritz Olympique
Pool 3 winners - ASM Clermont Auvergne
Pool 4 winners - Stade Français Paris
Pool 5 winners - Toulouse
Pool 6 winners - LeinsterThe two best Pool runners-up are:
Pool 2 runners- up - Ospreys (20 points)
Pool 1 runners-up - Northampton Saints (19 points)