Forced to chase a 10 point deficit, they never seemed likely of running it down.
For Saracens there will be satisfaction, too, having extracted revenge after losing their last three European matches against Leinster, including last year's quarterfinal. They also finish this nine-match tournament unbeaten, only the third side to do so.
Accolades will go to Billy Vunipola for his decisive try 13 minutes from time but defensively, to a man, Saracens were superb.
Leinster's favoured wrap around plays were, for the most, nullified. Try as they might they could only breakthrough for one try to prop Tadhg Furlong when Saracens were reduced to 14 men.
Big moments, there were plenty.
Welsh star Liam Williams pulled off a spot tackle and turnover in the same movement to halt Leinster in the 22. With a diving intercept on the tips of his fingers, inches from yellow card offence, Vunipola produced another vital stop.
Saracens played with fast tempo and intent to use the width, posing the greater attacking threats throughout.
Alex Lozowski looked dangerous early but Leinster worked their way back by controlling possession and building phases, as they so often do.
Saracens imposed their presence physically – in the end this the difference. Will Skelton, Vunipola, Jamie George and George Kruis dominated collisions, pushing the Leinster ball carriers back on several occasions.
After 20 phases with minimal gain, one Rob Kearney bust changed the complexion of the match.
Cian Healy was held up but the damaged had been done with Itoje yellow carded for three successive penalties on Saracens line. Hammering away, eventually Furlong crashed over to celebrate his 100th appearance.
At that point, 10 points down, Saracens were on the ropes. Itoje was joined by starting props Mako Vunipola (hamstring) and Titi Lamositele (ankle) on the sideline after half an hour, giving Leinster the firm upper hand.
Saracens remained calm, composed themselves, as all quality teams do, to earn a breakdown penalty to chip away at the lead.
When former Crusaders wing Sean Maitland struck on half time after slick soft hands from Owen Farrell, suddenly it was all square.
Scott Fardy's yellow card for repeated infringing 58 minutes into the second half gave Saracens the chance to pull clear – and Billy Vunipola took full advantage. Charging off the back of the scrum, the powerhouse English No 8 never looked like passing, beating four defenders on his way over.
From there, Saracens were too good.
The English champions now have the chance to pull off the double act.
Few would bet against them achieving that feat, too.
Their main challenge now may come from the English salary cap auditors.
Scorers:
Saracens 20: Sean Maitland, Billy Vunipola tries, Owen Farrell pen 2, con
Leinster 10: Tadhg Furlong try, Johnny Sexton pen, con
HT: 10-10
