|London Irish (20) 43|
|Tries: Lewington, Penalty, Guest, Cross, Fenby, Dorrian Cons: Geraghty, Homer Pens: Geraghty 3|
|Grenoble (27) 41|
|Tries: Bouchet 2, Caminati, Marrou Cons: Hart3 Pens: Caminati 2 Hart 2 DG: Caminati|
London Irish overcame Grenoble to win their first match since boss Brian Smith's departure, despite playing more than 20 minutes with 14 men.
They led through Alex Lewington and a penalty try before Laurent Bouchet's brace helped put Grenoble ahead.
Tom Guest's touchdown for the Exiles cut the margin to 27-20 at the break.
Geoff Cross's try following David Paice's red card and late scores from Andrew Fenby and Myles Dorrian helped seal a dramatic Challenge Cup win.
Julien Caminati and Louis Marrou had both gone over for the visitors to open up a 10-point lead with 10 minutes remaining.
London Irish, under the guidance of interim head coach Glenn Delaney, moved back to the top of Pool One with the bonus-point triumph ahead of Cardiff Blues, who thrashed Rovigo 104-12 on Friday night.
|London Irish's fine home form against the French|
|Irish have lost only one of their last 19 matches, winning 17, at home to French opposition.|
The Exiles got off to a lively start, with full-back Fenby particularly menacing as he was held up over the line after putting Lewington over for the game's first points.
London Irish's second score came soon after with the pack asserting their dominance to earn a penalty try.
However, Bouchet stunned the hosts with a quick-fire brace to help level the scores at 12-12.
Caminati landed two penalties and James Hart added a third to put the Top 14 side in control before Shane Geraghty slotted a three-pointer in response.
Versatile back Caminati then booted a remarkable drop-goal from 42 metres out and Hart teed up his third kick of the game to open a 12-point lead, only for Guest to power over for Irish just before the break.
Geraghty reduced the margin to one point with two penalties after the interval before Grenoble found themselves momentarily down to 13 men, following the sin-binning of Jonathan Owen and Mahamadou Diaby, the latter for a high hit on Lewington.
Irish failed to make the most of their numerical advantage and found themselves a man down themselves when Paice was sent off.
Converted Caminati and Marrou efforts looked to have put the match beyond doubt, but in a thrilling finish at the Madejski Stadium, the Exiles kept their European ambitions alive as Fenby crossed and Tom Homer added the extras to Myler's try to secure victory.
London Irish: Fenby; Ojo, Mulchrone, Sheridan, Lewington; Geraghty, Steele; Court, Paice, Aulika; Skivington (capt), Sinclair; Guest, Cowan, Treviranus.
Replacements: Stevens, Halavatau, Cross, Leo, Low, O'Leary, Dorrian, Homer.
Grenoble: Caminati; Caire, Mignot, Messina, Kilioni; Michallet, Hart (capt); Dardet, Bouchet, Owen; Hand, Skeate, Rey, Diaby, Faure.
Replacements: Jammes, Coulson, Edwards, Goze, Marrou, Henry, Saseras, Gelin.
Referee: Dudley Phillips (Ireland)