Saints produced a sensational derby-day display as they cut Leicester Tigers apart to claim a stunning 29-15 win at Welford Road on Friday night.
It was the second season in succession that the black, green and gold had won at the home of their rivals, but this was far more clear-cut than the 27-21 triumph last April.
Saints were in control from start to finish as two Tom Collins tries and one from man of the match Cobus Reinach propelled them into a lead that they never looked likely to relinquish.
Dan Biggar added 14 points with the boot as Leicester were left totally deflated by their old foes, who had produced one of the best away displays in the club's history.
The only disappointment for Saints was that they didn't manage to claim the try bonus point on a night when they were totally dominant.
But another win at Welford Road was more than satisfactory as they moved up to fifth in the Gallagher Premiership, just five points behind fourth-placed Gloucester.
Saints had gone into the derby on the back of winning the Premiership Rugby Cup at Franklin's Gardens last Sunday.
And they showed their belief early on, getting off to a flying start as Ahsee Tuala sent Collins through a gap and the speedy wing tormented the Tigers defence before setting the onrushing Reinach free to score his 15th try of the season.
Boos rang out as the Tigers fans felt Taqele Naiyaravoro had knocked the ball on near his own 22 in the build-up, but it wasn't given by referee Wayne Barnes and Saints led 5-0, with Biggar having sent the conversion just to the left of the posts.
Tigers threatened to respond immediately but Reinach was in action at the other end, making a brilliant last-ditch tackle to stop Sam Aspland-Robinson scoring in the corner.
Saints were suddenly under siege and after Naiyaravoro knocked the ball out of play, Tigers ramped up the pressure, winning a penalty, which George Ford kicked.
But after Mike Williams cynically killed the ball with Saints on the charge again, the Leicester flanker was sent to the sin bin.
Biggar kicked the resulting penalty and he was soon converting a Collins score as Saints once again scythed through the home side, with Rory Hutchinson opening the door superbly.
There were grumbles of discontent among the home fans as their side found themselves 15-3 down, and those groans grew louder when Saints put together another masterpiece before the break.
Teimana Harrison made a huge break and Hutchinson lofted an eye-catching long pass out to Naiyaravoro, with the big winger doing really well to get his offload away to the waiting Collins before being bundled out of play. Collins did the rest.
Biggar sent the conversion wide, but Saints led 20-3 with seconds to go in the first half.
There was still time for some Tigers pressure, but Saints won a key penalty at the home side's scrum to bring an end to an incredible first half.
And there was another black, green and gold penalty early in the second period, allowing Biggar to extend the lead to 23-3.
The fly-half was soon adding another three points to the tally after Dan Cole was sin-binned for slapping the ball out of Reinach's hands just in front of the posts.
Leicester were really struggling with their discipline, giving away penalty after penalty.
Biggar slotted another kick to make it 29-3 and the Saints voices were the only ones that could be heard at a largely gloomy Welford Road.
The bonus point was almost secured when Biggar dotted down, but Alex Moon's final pass to the fly-half was rightly deemed forward and there was no try.
Saints were still in control but Tigers eventually managed to find a way through the resilient away defence as Ford danced across the line and spotted a gap to score.
The fly-half converted to cut the gap to 19 points with little more than 12 minutes remaining.
And after Jamie Gibson was sin-binned late on, Youngs managed to muscle his way over.
But there was more of a grimace than a celebration from the Tigers skipper at the end of an awful night for his team.
Saints didn't care though as they celebrated again at Welford Road.
Leicester Tigers: Olowofela; Aspland-Robinson, Tuilagi (Owen 69), Eastmond (Toomua 40), May; Ford, Harrison; Genge (Gigena 72), T Youngs (c), Cole (Heyes 78); Spencer, Kitchener; Williams (Kerr 70), O'Connor (Fitzgerald 61), Thompson.
Saints: Tuala; Collins, Hutchinson, Francis, Naiyaravoro (Furbank 57); Biggar, Reinach (Mitchell 67); Van Wyk (Waller 40), Fish (Marshall 65), Hill (Franks 62); Moon, Ratuniyarawa (Craig 74); Gibson, Brüssow (Wood 62), Harrison (c).
Referee: Wayne Barnes