A late Olly Barkley penalty helped give Racing Metro an unlikely 22-17 Heineken Cup victory over Munster at a wet and soggy Stade de France.
Simon Zebo looked like he had earned the visitors the points with a brilliant 73rd-minute solo try, but when Conor Murray was penalised for holding on inside his 22 with three minutes left, Barkley held his nerve to slot over.
Mirco Bergamasco, kicking while Barkley received treatment, then struck another penalty in the final minute to give the French club a famous first win.
Sean Dougall's 15th-minute try had helped Munster take a 10-0 lead, while Ronan O'Gara passed 1,300 Heineken Cup points as Munster took charge.
But when Doug Howlett failed to collect a low pass from O'Gara, home scrum-half Maxime Machenaud chased through for a try after 31 minutes. Having converted that try, Barkley slotted over a penalty to give Racing a 13-10 half-time lead.
After a scrappy start to the second half in muddy conditions, Racing's latest signing struck another huge penalty to extend the home side's advantage
But, just when it looked like Racing might hold on, Zebo scored with seven minutes left and Ian Keatley's conversion from wide out on the left put Munster 17-16 in front.
However, two late infringements cost Munster dear as Racing stole the points.
Defending champions Leinster were left clinging on for a nervy 9-6 win over competition debutants Exeter Chiefs at the RDS.
Argentina international Ignacio Mieres missed an injury-time penalty to earn a draw for Exeter as Jonathan Sexton's nine-point haul proved to be just enough for the 2009, 2011 and 2012 winners.
Led by man-of-the-match Tom Hayes, the Chiefs played the better rugby for much of a tryless Pool Five opener and looked right at home in Europe's top tournament.
However, fly-half Gareth Steenson missed two of his four penalty attempts as his opposite number Sexton helped Leinster squeeze home.
Charlie Hodgson led the way with a 25-point haul as Saracens launched their campaign by dismantling Edinburgh 45-0 at Murrayfield.
Hodgson scored one of five tries - Joel Tomkins, Owen Farrell, Chris Ashton and Alex Goode claimed the others - and booted four penalties and four conversions as Edinburgh were completely outclassed.
Saracens were on top right from the start and former rugby league star Tomkins marked his Heineken Cup debut by claiming the opening try.
And even when Sarries were down to 14 men following the second-half sin-binning of Schalk Brits, Edinburgh failed to make an impression.
Harlequins overcame the early loss of Nick Evans to make a triumphant start, winning a bruising clash with Biarritz 40-13.
Evans, the Premiership champions' ringmaster, limped off just 17 minutes into the evening with his left ankle heavily strapped and was later using crutches.
But even without him, Quins were able to subdue Biarritz with his replacement Ben Botica proving a highly-capable deputy in a bonus-point victory.
Botica, who joined Quins this season and is the son of rugby league great Frano, kicked 18 points and showed a promising level of composure.
Tries from Danny Care, Rob Buchanan, Jordan Turner Hall and Seb Stegmann also helped ensure the tournament's fifth favourites escaped a third successive defeat.
Biarritz's points came from a Arnaud Heguy try and the boot of Julien Peyrelongue.
Morgan Stoddart's first-half red card saw a spirited Scarlets' challenge end in a comprehensive 49-16 defeat at Clermont Auvergne.
The Welsh side were more than competitive for the first 37 minutes, but Stoddart's dismissal for a second yellow effectively ended their hopes.
The scores were level at 13-13 when the Wales wing - who was making just his second appearance since a 15-month injury lay off - saw red, but last season's beaten semi-finalists ran away with game after that to secure a comprehensive bonus-point success.
Jon Davies' early try was the highlight for the Scarlets but Clermont crossed for six scores of their own, with Damien Chouly, Lee Byrne, Julien Bonnaire, Napolioni Nalaga and a penalty try adding to Sitiveni Sivivatu's first-half score.
Connacht made a winning start with a scrappy 19-10 victory away to tournament newcomers Zebre in Parma.
John Muldoon's 62nd-minute try proved vital for the visitors, who had dominated the third quarter but were starting to look like they would rue a series of missed opportunities in the home 22.
Connacht's former Scotland fly-half Dan Parks added the remainder of his side's points from four penalties and a conversion.
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