Grenoble, who were stripped of the match points from their 20-9 win against the same opposition in Round 3 after being found guilty of fielding an ineligible player, took the lead with a penalty goal from Valentin Courrent and the scrum-half quickly added a conversion.

That kicking opportunity came courtesy of hooker Laurent Bouchet crossing the Exiles' line - and the front row forward proved that was no fluke when he added another just eight minutes later.

Outside-half Alex Davies kept London Welsh in touch up to the break with two penalty goals but the gap was quickly opened up again just two minutes after the start of the second half when right wing Florian Ninard crossed and Courrent added the extra points to put them 16 points clear.

The inevitable flood of replacements produced more stop than start and replacement flanker Mike Denbee crossed for an Exiles try that Davies converted.

Feliuaki Taukeiaho got try number four in the 74th minute that earned Grenoble the bonus point but Paris can seal the group with a match to spare come Round 5 and their trip to Grenoble.