Leinster booked a berth in the European Champions Cup quarter-finals with two pool rounds to spare by thumping Premiership leaders Northampton 50-21.

Two Garry Ringrose tries plus Tadhg Furlong and Dave Kearney scores secured the bonus point before half-time.

Dan Biggar and Ollie Sleightholme did touch down for the Saints as they trailed 31-14 at the break.

Ringrose completed his hat-trick with James Lowe and Caelan Doris also scoring as Ahsee Tuala replied.

Benetton's 25-22 win over Lyon earlier in the day meant Leinster would become the first-ever team to qualify for the knockout stage after four pool games if they secured a four-try win and prevented the Saints from earning a bonus point.

With Ringrose, Lowe and Jordan Larmour producing some irresistible running rugby, Leinster had their four tries by the 36th minute and while the Saints notched three touchdowns of their own, they were unable to add another which would have mathematically kept the Irish province waiting to guarantee qualification.

Saints make eight changes for return contest

With England star Courtney Lawes and Owen Franks among a large contingent of injured Northampton players, Saints director of rugby Chris Boyd made eight changes from last weekend's 43-16 home defeat by the Irish province.

England World Cup squad player Lewis Ludlam, who normally plays at flanker, was selected at number eight with scrum-half Connor Tupai making his first Champions Cup start.

Leinster's five changes included Ross Byrne's inclusion in place of Johnny Sexton and the fly-half went on to produce an impressive match before being replaced after taking a knock in the second period.

Northampton started the game five points behind the Pool 1 leaders but their hopes of cutting into that margin suffered a couple of early blows.

Firstly, Ringrose charged down an attempted Andy Symons clearance to score a third-minute try after referee Dan Jones had called Northampton advantage following a Leinster knock-on.

Within three minutes, Ringrose was running in his second try after being set up by Lowe's delicious off-load, with Byrne adding his second set of extras before slotting another three points five minutes later.

To their credit, Northampton showed offloading skills of their own as Symons' superb no-look pass set up a Biggar try after the Wales fly-half had taken a quick tap-penalty following pressure in the Leinster 22.

But Leinster's bonus point was soon bagged with wing Kearney continuing his renaissance by charging in to score after Furlong had barged his way over, with the Saints down to 14 men on both occasions following indiscretions by full-back Tuala and captain Tom Wood, who was making his 200th appearance for the club.

Ludlam's long-busting run set up wing Sleightholme's try in first-half injury time as Leinster led 31-14 at the break but any slim prospects of a Saints fightback were ended as Lowe and Ringrose added further tries within eight minutes of the restart.

Tuala punished a rare moment of Leinster defensive slackness to run in unopposed under the posts in the 51st minute but they were unable to snatch a bonus point as the home side's impressive young number eight Doris completed the scoring.

Leinster: Larmour; D Kearney, Ringrose, Henshaw, Lowe; Byrne, McGrath; Healy, Tracy, Furlong, Fardy (capt), Ryan, Ruddock, Van der Flier, Doris.

Replacements: B Byrne, E Byrne, Porter, Toner, Deegan, Gibson-Park, Frawley, R Kearney.

Northampton: Tuala; Sleightholme, Proctor, Symons, Naiyaravoro; Biggar, Tupai; Van Wyk, Van Vuuren, Hill, Ratuniyarawa, Coles, Wood (capt), Gibson, Ludlam.

Replacements: Matavesi, Waller, Painter, Bean, Tonks, Mitchell, Grayson, Dingwall

Referee: Dan Jones (Wales)