Saracens suffered their first defeat of the Premiership season on Saturday as they went down to Harlequins 17-10 at the Stoop.
It was also second-row Maro Itoje's first loss for club or country since January 9 in a shock result.
A quick start from the hosts saw them take a 17-0 lead into half-time, but the visitors did manage to consolidate a late losing bonus point from a late Ben Spencer penalty.
The day belonged to Quins, whose second win of the season lifted them towards the upper echelons of the table, while Saracens dropped ground in the title race to reclaim their Premiership crown.
Quins made a storming start to the match, adding to Tim Swiel's seventh minute penalty with a converted try moments later.
Tim Visser made an interception close to the try line and raced forward to go over with Swiel kicking to send the hosts into double figures early on.
It got much better soon after as Swiel was once again involved. The second try of the afternoon came after the fly-half fed in Mike Brown who found Charlie Walker in space. He went over and Swiel made no mistake from the tee.
Saracens had the best of possession in the lead up to half time, but as much as they tried to get over the line and their name on the scoresheet, the home team held their own before a knock-on brought to an end the first 40 minutes.
However, Harlequins heroics were not evident at the start of the second half as Mark McCall's side responded as champions should. Mike Ellery collected a chipped ball on the wing before setting up Richard Wigglesworth to go over. Alex Lozowski's conversion ensured the perfect start to the second half for last season's Premiership winners.
With a quarter of the game remaining, Lowoski had a chance to at least garner Saracens a losing bonus point, but his penalty rebounded off the post and agonisingly out of play.
Just as Saracens looked to be running out of ideas, they were handed a lifeline when James Horwill was sent to the sin bin with five minutes remaining.
The visitors came within a converted try of their opponents when Spencer kicked through the posts, but it was too little, too late in terms of getting anything more than the solitary point.
Tries: Visser, Walker
Harlequins: 15 Mike Brown, 14 Charlie Walker, 13 Matt Hopper, 12 Jamie Roberts, 11 Tim Visser, 10 Tim Swiel, 9 Danny Care (c), 8 James Chisholm, 7 Luke Wallace, 6 Chris Robshaw, 5 James Horwill, 4 George Merrick, 3 Will Collier, 2 Rob Buchanan, 1 Joe Marler
Replacements: 16 Joe Gray, 17 Mark Lambert, 18 Kyle Sinckler, 19 Sam Twomey, 20 Dave Ward, 21 Karl Dickson, 22 Ruaridh Jackson, 23 Alofa Alofa
Saracens: 15 Alex Goode, 14 Mike Ellery, 13 Marcelo Bosch, 12 Brad Barritt (c), 11 Chris Wyles, 10 Alex Lozowski, 9 Richard Wigglesworth, 8 Billy Vunipola, 7 Jackson Wray, 6 Michael Rhodes, 5 Jim Hamilton, 4 Maro Itoje, 3 Petrus Du Plessis, 2 Schalk Brits, 1 Mako Vunipola
Replacements: 16 Jamie George, 17 Richard Barrington, 18 Juan Figallo, 19 Kelly Brown, 20 Scott Spurling, 21 Ben Spencer, 22 Nick Tompkins, 23 Matt Gallagher
Referee: Craig Maxwell-Keys
Assistant Referees: Nigel Carrick & Phil Watters
TMO: David Grashoff