Chris Ashton scored four tries to help Saracens to a thumping 68-17 win over London Welsh as they booked their place in the play-offs.
It started poorly for Welsh, who were reduced to 14 after just four minutes, Matt Corker finding himself sent to the bin after a fourth penalty in just a few seconds.
They were made to pay for that by Billy Vunipola, who expertly went through a catch and drive to spear their way past the Welsh backline.
Owen Farrell embarked on his first successful kick of the afternoon, one of many by full-time. But Welsh did fire back not long after, equalling the scores via Nic Reynolds.
He combined well with Tom May, after the centre made the break forward as Chris Elder added the extras.
Not that the scores were level for long, as Saracens grabbed their second through David Strettle, after he emerged from a well fought scrum to go over in the corner, Farrell again doing the business.
Welsh again contested after that setback, and Elder's penalty reduced the scores to four, though that lasted little time.
The other Vunipola, Mako, got Saracens third of the half, going in underneath the posts in a frantic opening half of rugby. And it only got more exciting, because Welsh got their second of the afternoon through Elder, who burst forward surrounded by team-mates from the restart to ensure Saracens were once again pegged back. His conversion again reduced Saracens lead to four.
But crucially on the brink of half-time, the visitors went over for number four, and it was the first of the afternoon for Ashton. He collected a catch and drive inside the corner before powering through to give Sarries an all important half-time lead.
After that first half of all action, you could be excused for thinking it would be another equal half. But Alex Goode gave an inclination of what was to come, grabbing his try after a quickly taken penalty, Farrell extending the lead.
On the hour mark came the sixth try, Juan Figallo barging his way through bodies to pour on the misery, misery which was added to once again by Ashton just two minutes later.
Saracens looked like scoring from every attack, and Ashton pretty much did for the rest of the game. Lovely interplay from Farrell and Goode eventually saw Ashton take over, Farrell finishing off that move. And he did so again three minutes later, sealing his hat-trick in the process, the quickest ever in Premiership history.
Goode was again the provider, his defence splitting pass leaving Ashton to do the basics, Farrell continuing his almost perfect record in front of the posts.
And an incredible afternoon got even better for the Saracens and England winger Ashton, who scored his third try in less than ten minutes to enhance what was turning into a horrible afternoon for the already relegated Welsh.
The tenth and final try came from Charlie Hodgson five minutes from time, finishing off a superb side-stepping solo effort in the corner, allowing Farrell to kindly and finally finish off the scoring for Saracens, who secured their play-off place in the process of this crushing victory. Saracens will face off against Northampton at Franklin's Gardens.
For London Welsh:
Tries: Reynolds, Elder
Cons: Elder 2
Yellow Card: Corker
Tries: B. Vunipola, Strettle, M. Vunipola, Ashton 4, Goode, Figallo, Hodgson
Cons: Farrell 9
London Welsh: 15 Seb Jewell, 14 Alan Awcock, 13 Nic Reynolds, 12 Tom May (c), 11 Chris Elder, 10 Olly Barkley, 9 Rob Lewis, 8 Opeti Fonua, 7 Darren Waters, 6 Ben West, 5 Matt Corker, 4 Josh McNally, 3 Jack Gilding, 2 Koree Britton, 1 Eddie Aholelei.
Replacements: 16 Nathan Morris, 17 Nathan Trevett, 18 Ben Cooper, 19 Daniel Browne, 20 Richard Thorpe, 21 Paul Rowley, 22 Will Robinson, 23 Seb Stegmann.
Saracens: 15 Alex Goode, 14 Chris Ashton, 13 Marcelo Bosch, 12 Chris Wyles, 11 David Strettle, 10 Owen Farrell, 9 Neil De Kock, 8 Billy Vunipola, 7 Jacques Burger, 6 Jackson Wray, 5 Alistair Hargreaves (c), 4 George Kruis, 3 Petrus Du Plessis, 2 Schalk Brits, 1 Mako Vunipola.
Replacements: 16 Jamie George, 17 Rhys Gill, 18 Juan Figallo, 19 Maro Itoje, 20 Kelly Brown, 21 Richard Wigglesworth, 22 Charlie Hodgson, 23 Duncan Taylor.
Venue: Kassam Stadium
Referee: Luke Pearce
Assistant Referees: Darren Gamage, Nigel Carrick
TMO: Trevor Fisher