|Grenoble (3) 3|
|Cardiff Blues (7) 28|
|Tries: L Williams, penalty try, penalty try, Navidi Cons: Anscombe 3, G Davies|
Cardiff Blues battered their way to a 28-3 bonus point win in Grenoble, but they finished second in Pool 1.
London Irish topped the Challenge Cup group with a 34-6 win in Rovigo.
Lloyd Williams' close range try and Gareth Anscombe's conversion, with a James Hart penalty in reply, gave Blues a 7-3 lead at the break.
Blues won two penalty tries from scrums in the second period, Anscombe goaling both and Josh Navidi's late pushover try was converted by Gareth Davies.
Blues and Irish will not know their quarter-final opponents until the round's remaining games are completed.
The visitors went into the match knowing they already had a last eight place booked courtesy of Edinburgh's 38-20 victory over Bordeaux-Begles on Friday.
But they fielded a more powerful team than in the previous romp against Rovigo, with Alex Cuthbert, captain Gethin Jenkins and Sam Warburton among those returning for a last regional appearance before Wales' 2015 Six Nations campaign.
A hardy band of Blues supporters had also braved the freezing temperatures more suited to the skiers tackling the snow-capped Alps in the background.
Sleet began falling around half an hour before kick-off to make conditions even more uncomfortable.
Blues turned down early kickable penalties, but a misfiring set-piece cost them vital chances and it took 27 minutes to break the deadlock as scrum-half Williams jinked his way over at close quarters for Anscombe to convert.
Irish scrum-half James Hart opened the home account with a penalty after 33 minutes to make it 7-3, but it was Cuthbert who created the only other action of the half with a storming run from halfway which ended just short of the try-line.
Conditions deteriorated during the second half with the snow getting thicker at times and the Blues penning Grenoble in their own 22 for the periods.
Hooker Loick Jammes was sin-binned for an offence close to the line and with the home pack in disarray, the Blues forced a penalty try after 55 minutes, converted by Anscombe.
They repeated the trick on 71 minutes with another converted penalty try, this time with replacement back-rower Fabien Alexandre in the bin.
By this stage London Irish had bagged their own bonus point victory to end the Blues' hopes of winning the group.
But the Welsh region turned the screw to earn the extra point after 78 minutes when Navidi finished off a pushover try.
The players were relieved to head for the dressing room in the bitter cold, with the Welsh side assured of finishing as best runners-up and sixth seeds for the quarter-finals.
Grenoble: Fabien Gengenbacher (capt); Ratu Alipate Ratini, Jackson Willison, Louis Marrou, Daniel Kilioni; Jordan Michallet, James Hart; Rémy Hugues, Loick Jammes, Dayna Edwards, Ben Hand, Ross Skeate, Henry Vanderglas, Mahamadou Diaby, Florian Faure.
Replacements: Alexandre Dardet, Denis Coulson, Richard Choirat, Thibault Rey, Fabien Alexandre, Joannes Henry, Geoffroy Messina, Benjamin Thiery.
Cardiff Blues: Rhys Patchell; Richard Smith, Cory Allen, Adam Thomas, Alex Cuthbert; Gareth Anscombe, Lloyd Williams; Gethin Jenkins (capt), Kristian Dacey, Taufa'ao Filise, Chris Dicomidis, Filo Paulo, Josh Turnbull, Sam Warburton, Josh Navidi.
Replacements: Matthew Rees, Sam Hobbs, Adam Jones, Macauley Cook, Ellis Jenkins, Tavis Knoyle, Gareth Davies, Gavin Evans.
Referee: David Wilkinson (Ireland)
Touch judges: Kieran Barry, Brian MacNeice (Ireland)
Fourth official: Francois Bouzac (France)