London Irish produced a shock 22-13 win over league leaders Saracens at Allianz Park on Saturday, scoring three first-half tries.
Sarries were seeking a response following a narrow home reverse against Northampton, while had been handsome victors against Scarlets.
James O'Connor's early penalty gave the visitors an advantage, but that was cancelled out on 13 minutes when Marcelo Bosch grabbed his first try for the club, after Saracens opted to attack their opponents' line from a penalty.
The Exiles hit back at the beginning of the second quarter through Matt Parr's try, created by an exciting series of offloads. O'Connor added the conversion.
Charlie Hodgson's penalty goal on 34 minutes made it 8-10, but Irish struck a hammer blow before half-time.
First, Alex Lewington raced away to score a fine try, and then he provided a grubber kick for George Skivington to latch onto and regather to touch down.
O'Connor converted the final try of the half to make it 8-22 at the interval. There were fewer points scored in the second half, with Irish content to sit on their lead and stifle any threat of a comeback.
And the visitors actually enjoyed the lion's share of attacking chances, as Sarries struggled to mount any sort of threat in the attacking quarter.
They eventually made it over five minutes from the end when Schalk Brits crossed, though Hodgson was wide with the conversion and there wasn't enough time for Saracens to get themselves back into the game.
Tries: Bosch, Brits
Tries: Parr, Lewington, Skivington
Cons: O'Connor 2
Yellow Cards: Mulchrone, Cowan
Saracens: 15 Ben Ransom 14 Chris Ashton, 13 Marcelo Bosch, 12 Chris Wyles, 11 David Strettle 10 Charlie Hodgson, 9 Neil de Kock, 8 Ernst Joubert 7 Jacques Burger, 6 Jackson Wray, 5 Mouritz Botha, 4 Steve Borthwick (c), 3 Matt Stevens, 2 Jamie George, 1 Richard Barrington.
Replacements: 16 Schalk Brits, 17 Rhys Gill, 18 James Johnston, 19 George Kruis, 20 Matt Hankin, 21 Richard Wigglesworth, 22 Joel Tomkins, 23 Jack Wilson.
London Irish: 15 James O'Connor, 14 Alex Lewington, 13 Fergus Mulchrone, 12 Eamonn Sheridan, 11 Andrew Fenby, 10 Shane Geraghty, 9 Tomás O'Leary, 8 Ofisa Treviranus, 7 Blair Cowan, 6 Kieran Low, 5 George Skivington, 4 Nic Rouse, 3 Jamie Hagan, 2 David Paice, 1 Matt Parr
Replacements: 16 Jimmy Stevens, 17 John Yapp, 18 Leo Halavatau, 19 Jebb Sinclair, 20 Gerard Ellis, 21 Tom Fowlie, 22 Ian Humphreys, 23 Sean Kennedy
Referee: Dean Richards
Assistant Referees: Nigel Carrick, Andy Watson
TMO: Keith Lewis