London Irish qualified for the quarter-finals of the European Challenge Cup as top seeds following their 23-9 Pool One win at Rovigo.
Tries from Kieran Roche, Adam Thompstone and Dominic Shabbo held off a stubborn effort from the Italians.
Roche set the second-string Exiles on their way before half-time at the Stadio Mario Battaglini.
But the visitors' were reduced to 14 men when lock Gary Johnson was sin-binned and three penalties from German Bustos kicked Rovigo back into the game.
Toby Booth's men went back in front when Shane Geraghty added a 57th minute penalty
before Thompstone gave the Guinness Premiership side breathing space.
It was only the 21-year-old academy wing Thompstone second try at senior level and the Exiles maintained their unbeaten run when Shabbo crossed three minutes from time to confirm their status as top seeds.
Northampton finished as second seeds after keeping up their 100 per cent record in the Challenge Cup following a routine seven-try victory over Toulon.
Number eight Mark Easter, brother of England forward Nick, scored in either half to set the Saints on their way to a fifth bonus-point at Franklin's Gardens.
Jim Mallinder's men moved through the gears in the second half, adding six tries including braces for wing Chris Ashton and prop Soane Tonga'uiha.
Fly-half Stephen Myler scored an impressive 18-point haul including a try, five conversion and a penalty.
Myler and David Vidal exchanged early penalties but Toulon were on the back foot after scrum-half Matthew Henjak was sin-binned on 24 minutes.
Easter scored a pushover try for the opener three minutes later but the visitors hit back through skipper Mafileo Kefu's try to reduce the lead to 10-0 at the break.
But Northampton applied the pressure in the second half and after Tonga'uiha added the third try in the 42nd minute, the Tongan and Ashton scored doubles in between Myler's touch down.
Worcester secured a home quarter-final draw against Brive in the Challenge Cup following their emphatic 68-17 success over Petrarca to top Pool Three.
The Warriors ran in ten tries to overtake their last eight opponents from France amid speculation head coach Clive Griffiths is set to quit the club for 'personal reasons' next week.
Joe Carlisle opened the floodgates as early as the seventh minute to set up a convincing victory at Sixways.
The Warriors stormed into a 40-0 half-time lead through tries from Rico Gear, Charlie Fellows, Will Bowley, Kai Horstmann and Dale Rasmussen.
Ex-Gloucester fly-half Ludovic Mercier hit back as Petrarca looked to restore their pride but two penalty tries from scrums allowed Kitch Kitchener and Hal Luscombe to complete the rout.
