London Irish (15) 23 Tries: Ojo Pens: Lamb 4, Armitage Drop-goals: Lamb Munster (6) 17 Tries: Tuitupou Pens: O'Gara 4
Tuitupou (front) earned Munster a bonus point
London Irish opened their Heineken Cup campaign with victory over Munster but the visitors claimed a last-gasp losing bonus point through Sam Tuitupou.
Irish led 15-6 at the break via four penalties and a drop-goal from Ryan Lamb to two Ronan O'Gara penalties.
A Topsy Ojo interception try saw the Exiles pull clear in the Pool 4 match.
Two O'Gara penalties reduced the margin and although Delon Armitage kicked a massive penalty, Tuitupou's late try sent Munster home reasonably happy.
The win, in front of over 20,000 at the Madejski Stadium, sends London Irish top of the pool ahead of Jonny Wilkinson's Toulon, who needed a late Paul Sackey try to beat the Ospreys in the south of France.
After a disappointing 2009-10 season London Irish have been rejuvenated this term and although the Premiership leaders are renowned for the potency of their attacking play, they had to rely on a powerful defensive effort to see off their Magners League counterparts, and two-time Heineken Cup champions, Munster.
They managed to hold out until deep into the final minute, when O'Gara slid a precise grubber kick through the London Irish thin green line and Tuitupou touched down.
The reliable boot of O'Gara had chipped the visitors into an early lead but Lamb soon landed two of his own to edge the hosts ahead.
The home side were looking sharp with ball in hand, with Peter Stringer and Ojo both making good ground in breaks down the right.
They could not cross the visitors' line but a third Lamb penalty, with Munster's Tuitupou in the sin bin for a spear tackle on Stringer, followed by a short-range drop-goal, gave the hosts a 12-3 lead.
Further pressure from the Exiles yielded a fourth penalty but a head-high tackle by Delon Armitage on the flying Doug Howlett enabled O'Gara to trim the gap to 15-6 at the break.
Lamb hit the post with a drop-goal attempt seconds before the interval but the hosts extended their advantage straight after the restart as sometime England winger Ojo picked off an interception and showed a clean pair of heels as he strode over from halfway for an unconverted try.
With 25 minutes remaining O'Gara, who had earlier narrowly missed with a long-range attempt, landed his third penalty for Munster after the visitors pack won a scrum against the head.
For most of the final quarter Munster hammered away unsuccessfully, with Tony Buckley held up over the line by a superb Armitage tackle.
O'Gara cut the gap with a fourth penalty with 12 minutes to go and the Ireland fly-half's trusty boot put the ball on a plate for Tuitupou in the final seconds.
O'Gara could not add the conversion but the visitors will be pleased with a bonus point, while London Irish were delighted to have lowered the colours of one of the giants of the European game.
London Irish coach Toby Booth told BBC Radio Berkshire: "You play the game to win, we got rewarded for being persistent. We were delighted from an historical point of view and for our fans and for the Irish contingent.
"You saw what it meant to the players. As a coach that's all you can ask for. But we can't get carried away with the win but we'll enjoy it.
"If the boys put in a similar performance next week then it will give themselves and the fans something to be proud of. The fans were fantastic today, both sets played their part. Having people here cheering spurs us on and makes a massive difference."
Munster fly-half Ronan O'Gara: "I don't think we deserved to win, we weren't accurate enough to win.
"We're disappointed with some aspects but we fight to the end and we showed that again.
"Our discipline was a major issue for the first 40, and at this level you can't afford to have a player sent to the sin bin - although strangely that was probably our best period.
"We weren't accurate enough in the green zone. We've a few new combinations up front and they will take time to bed in. It's small margins that make the difference and we were found out by them."
London Irish: D Armitage; Ojo, Seveali'i, Mapusua, Tagicakibau; Lamb, Hodgson; Dermody, Buckland, Rautenbach, Kennedy, Casey, Roche, Danaher, Stowers.
Replacements: Allinson for Seveali'i (70), Garvey for Tagicakibau (69), Paice for Buckland (56), Corbisiero for Rautenbach (56), Joseph for Casey (69), Hala'ufia for Danaher (52).
Not Used: Lahiff, Bowden.
Munster: J Murphy; Howlett, Earls, Tuitupou, D Hurley; O'Gara, Stringer; Du Preez, Varley, Buckley, O'Callaghan, D. Ryan, Leamy, Ronan, Coughlan.
Replacements: Warwick for Earls (69), Williams for Stringer (73), Hayes for du Preez (64), Horan for Buckley (64), O'Driscoll for D Ryan (56), Wallace for Ronan (32).
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