Pat Lam's Bristol Bears sit second in the Premiership after missing a chance to draw level with Saints last weekend.
Bristol captain Steven Luatua and Charles Piutau, who scored one of his side's four second half tries, starred for the Bears but it wasn't enough to kick clear as London Irish first five-eighth Stephen Myler kicked a late penalty and snatch a 27-27 draw.
Waisake Naholo continued to endear himself in his new rugby home with a 60 metre intercept try for London Irish.
"It was frustrating," Lam said. "As I said to the boys before the game, we were in a situation that is certainly unfamiliar for Bristol where we had a chance to go top of the table and everyone expects us to win.
"With a minute and a half to go we had the five points but unfortunately we left most of them out there. There were a lot of good things, but we also have a lot of learning to do. We need to be ruthless and convert more points, particularly against a team like London Irish."
Sean Maitland scored the only try of the match as Saracens welcomed back their superstar roster to gain a 25-12 away win over Bath.
Maro Itoje and Billy Vunipola returned and Owen Farrell kicked 20 points in his first Premiership match since the World Cup but the win is only the start of a long road to starve off relegation after Saracens were docked 35 points for their salary cap breaches.
Several Kiwis at Wasps are enduring another difficult campaign – their latest 38-3 loss to Exeter in which they conceded five tries leaves them languishing in 10th with one win.
Promising playmaker Jacob Umaga, the nephew of Tana who recently extended his contract, kicked Wasps' only points and Jimmy Gopperth started at second five while Lima Sopoaga came off the bench.
Malakai Fekitoa and Brad Shields were absent due to injuries.
Over in the unpredictable French Top 14, Vern Cotter's Montpellier stunned league leaders Lyon 33-8 to move into fourth position with four wins and two draws from 10 games.
Jono Gibbes and Ronan O'Gara's La Rochelle returned to winning ways with their side's 22-13 victory over Castres.
Seta Tamanivalu came off the bench and Bristol recruit Semi Radradra scored as their Bordeaux side upset Racing 92 with a 34-30 win in Paris.
Former Auckland wing Bryce Heem started at fullback in Toulon's 19-9 away win over Pau which lifted Julian Savea and Liam Messam's club to fifth.
Loni Uhila, Fritz Lee, Tim Nanai-Williams and Faifili Levave all contributed to Clermont's dominant 30-13 win over Agen that maintained their contender status in third.
In the Pro 14, Dave Rennie's Glasgow Warriors dropped to fourth after being humbled 23-10 by traditional pace setters Leinster.
Previous Hurricanes team-mates Sam Lousi started in the second row and Blade Thomson at No 8 as Brad Mooar's Scarlets suffered a 29-5 away loss to Ulster.
Former Highlanders wing Matt Faddes claimed one of Ulster's four tries from centre as they moved into second in their conference.
Cardiff Blues, with Ray Lee-lo in the midfield, handed Benetton a shock 31-28 home loss to claim their third win of the season.
Domestic competitions take a backseat this week as European rivalries resume.
