Saracens made it four wins from four in the Aviva Premiership after they battled past title rivals Harlequins 22-12 at Twickenham Stoop on Saturday.
Both teams headed into the game in good form, with Harlequins having comfortably dispatched of Worcester, and Saracens sweeping all before them in the opening weeks of the new season.
The first points of the afternoon came just four minutes after the kick-off as Nick Evans punished home indiscipline to boot his team in front.
He added a second three-pointer less than ten minutes later after Sarries' Alex Goode had been dispatched to the sin-bin.
Owen Farrell hit back quickly to reduce the deficit to three points with his first penalty of the afternoon, and he added a second just three minutes before half-time, though it was sandwiched between two more from Evans, making it 12-6 to Harlequins at half-time.
But Sarries emerged for the second-half in ruthless mood, and an efficient display in attack coupled with a stern defensive performance steered them to victory.
The game's first and only try was scored by Chris Ashton on 51 minutes after the TMO ruled that a pass in the build-up did not go forward. Farrell added the conversion and he kicked three further penalties in the 15 minutes that followed to put further daylight between the two sides.
Quins rallied and pushed for the points they needed to get back into the game, but Sarries had the answer to the hosts' questions, and held on for an important win to continue their strong start to the new season.
Pen: Evans 4
Pen: Farrell 5
Harlequins: 15 Mike Brown, 14 Tom Williams, 13 George Lowe, 12 Tom Casson, 11 Ugo Monye, 10 Nick Evans, 9 Danny Care, 8 Tom Guest, 7 Chris Robshaw (c), 6 Maurie Fa'asavalu, 5 George Robson, 4 Nick Easter, 3 Will Collier, 2 Rob Buchanan, 1 Joe Marler
Replacements: 16 Dave Ward, 17 Mark Lambert, 18 Kyle Sinckler, 19 George Merrick, 20 Luke Wallace, 21 Karl Dickson, 22 Ben Botica, 23 Matt Hopper.
Saracens: 15 Alex Goode, 14 Chris Ashton, 13 Chris Wyles, 12 Duncan Taylor, 11 David Strettle, 10 Owen Farrell, 9 Richard Wigglesworth, 8 Billy Vunipola, 7 Jacques Burger, 6 Kelly Brown, 5 George Kruis, 4 Steve Borthwick (capt), 3 Matt Stevens, 2 Schalk Brits, 1 Mako Vunipola.
Replacements: 16 Jamie George, 17 Nick Auterac, 19 James Johnston, 19 Alistair Hargreaves, 20 Jackson Wray, 21 Neil de Kock, 22 Michael Tagicakibau, 23 Jack Wilson.
Referee: Martin Fox
Assistant referees: Gareth Copsey, Andy Watson
Television match official: Sean Davey
Timekeeper: Matthew Peters
Assessor: Brian Campsall