Tom Homer kicked 19 points London Irish bagged a crucial win in their fight against relegation by beating Saracens 29-16 at Madejski Stadium on Saturday.
The game was finely poised at the break with Homer and Sarries' Charlie Hodgson trading three penalties each.
But the Exiles put in an outstanding second half display and tries from Shane Geraghty and Ofisa Treviranus, aided by the accurate kicking of their full-back, sealed a potentially season-defining win.
David Strettle briefly gave the visitors hope, but it wasn't to be for the top-four contenders.
Irish have found it difficult throughout this season and went into the encounter just one point off bottom placed Sale.
However, they were facing a Saracens team that were severely depleted through international call-ups, and it showed. It proved to be a tight opening period with both teams struggling to find an attacking rhythm.
Hodgson did open the account with a penalty before Homer responded almost immediately with one of his own. The respective kickers then traded further three-pointers as the match remained finely poised at 6-6 after 14 minutes.
As the half neared its conclusion the hosts' full-back took them into the lead for the first time, but Hodgson was once again on target to level matters at the interval.
It was the Exiles that dominated the early passages of the second half. Homer's boot was once again to the fore as they moved 12-9 ahead before Geraghty touched down for a converted score.
Irish's kicker then added his fifth from the tee, but Strettle touched down for Sarries to reduce the deficit to 22-16.
However, the home side weren't to be denied and Treviranus crossed the whitewash to secure a crucial win in their battle to avoid the drop.
For London Irish:
Tries: Geraghty, Treviranu
Cons: Homer 2
Pens: Homer 5
Pens: Hodgson 3
London Irish: 15 Tom Homer, 14 Topsy Ojo, 13 Guy Armitage, 12 Shane Geraghty, 11 Marland Yarde, 10 Ian Humphreys, 9 Pat Phibbs, 8 Chris Hala'ufia 7 Jebb Sinclair, 6 Matt Garvey, 5 Bryn Evans (Captain), 4 George Skivington, 3 Halani Aulika, 2 Scott Lawson, 1 Max Lahiff.
Replacements: 16 Mike Mayhew, 17 Jerry Yanuyanutawa, 18Leo Halavatau, 19 Jamie Gibson, 20 Ofisa Treviranus, 21 Kieran Low, 22 Steven Shingler, 23 Jack Moates
Saracens: 15 Chris Wyles, 14 Joe Maddock, 13 Joel Tomkins, 12 Duncan Taylor, 11 David Strettle, 10 Charlie Hodgson, 9 Neil de Kock, 8 Ernst Joubert, 7 Will Fraser, 6 George Kruis, 5 Alistair Hargreaves, 4 Steve Borthwick (c), 3 Matt Stevens, 2 John Smit, 1 Nick Auterac.
Replacements: 16 Schalk Brits, 17 Rhys Gill, 18 Petrus du Plessis, 19 Mouritz Botha, 20 Jackson Wray, 21 Richard Wigglesworth, 22 Nils Mordt, 23 James Short.
Venue: Madejski Stadium
Referee: Andrew Small