A French battle between some of the most famous exiled names in Irish rugby went Racing 92's way as they halted Stade Francais's good start to the campaign.
Donnacha Ryan got one over on Paul O'Connell and Mike Prendergast - both on the Stade coaching team - in an enthralling clash at the Stade Jean-Bouin.
Simon Zebo was not in the panel but Ryan starred in a gritty Racing display.
Stade raced into a 10-3 lead as Kylan Hamdaoui crashed over and Morne Steyn nailed a penalty.
But Virimi Vakatawa’s response and two Finn Russell kicks got Racing going and though Steyn kept Stade ticking over off the tee, Russell was on point to help his side close it out 17-16 and move to within a point of their second-placed opponents.
Paddy Butler had the last laugh over fellow former Munster man Dave Ryan as Pau pulled off a hard-earned win at Agen.
The visitors earned a 28-25 success thanks to Antoine Hastoy's 23-point haul which included a late penalty to swing it.
It was another tough day at the office for Paddy Jackson's Perpignan.
Bottom of the table, they lost 23-20 on their own patch to Montpellier, with Jackson kicking two penalties and two conversions.
His old Ulster team-mate Ruan Pienaar shone for Montpellier, who moved up to sixth in the table.
Brendan Macken was the hero for Declan Kidney's London Irish who stole the win at the death against Coventry in the English Championship.
The visitors were 17-13 down heading for the closing minutes when Macken, a summer signing from Wasps, darted through the defence to crash over.
A Stephen Myler penalty put the seal on it as the Exiles made it four wins from four.
Geordan Murphy hailed Leicester Tiger fly-half George Ford's quality after he starred in a crucial Gallagher Premiership victory over Sale Sharks.
Ford kicked 14 points - landing all five of his shots at goal - to edge Leicester home 19-15 following successive Premiership losses against Wasps and Worcester.
"George's kicking statistics last season were in the 80s (%)," Leicester interim head coach Murphy said.
"For me, he's an 80%plus kicker and he is world class. He has been brilliant in the group.
"He's been doing a huge amount on and off the field, and you would expect as much from your international number 10. He is very important for us."
The Tigers avoided a third successive league defeat thanks to centre Kyle Eastmond's first-half try, plus four penalties and a conversion from Ford.