Saracens battled back from 17-0 down to beat Harlequins in a thrilling London derby at Twickenham Stoop.
Two tries in nine minutes from Cadan Murley gave Quins the ideal start, with Tommaso Allan adding a penalty before Elliot Daly and Max Malins hit back.
Joe Marchant's try saw Quins lead 24-12 at the break.
Malins' second try, another from Nick Tompkins and penalties from Owen Farrell and Daly, either side of a kick from Allan, sealed victory for Sarries.
While Sarries could call on England's Farrell, Maro Itoje, Billy Vunipola, Jamie George and Mako Vunipola, Quins failed in their attempt to have influential fly-half Marcus Smith cleared to play against his international team-mates because of rest period rules.
Any frustration Quins had over selections did not show early on as Murley demonstrated great pace to score two quick tries against last season's beaten Premiership finalists.
A long-range penalty from Allan - after the Italian landed both try conversions - opened a 17-point lead for the hosts, who lost prop Will Collier to injury moments before Saracens pulled a try back through Daly with what was their first real attack.
Malins then crossed to reduce the margin further, but Quins punished Sarries for an error on the counter-attack with Marchant going over.
A second Malins effort early in the second half was followed by a Farrell penalty before Tompkins' try gave Sarries the lead for the first time after 61 minutes.
An Allan penalty levelled things up at 27-27 just three minutes later, but Daly teed up the winning penalty with 14 minutes remaining.
'We knew it would create a kerfuffle' - Reaction
Harlequins director of rugby Tabai Matson:
On not being allowed to select Smith: "All we do is put a plan in and we get the thumbs up or thumbs down.
"We have a discussion and whether we get a thumbs up or thumbs down, they give us a reason. We accept that and move on.
"We knew that it was probably going to create a kerfuffle for our fans and for probably everyone looking in from the outside, but we can only move forward with the group that we have."
Saracens boss Mark McCall:
"We chose to start Maro, Billy and Owen and they were a big part of why we won. Jamie's and Mako's experience coming off the bench at this kind of place is good, but it was a good team performance.
"The process [to select England players following international duty] is simple really. There's a 10-week rule in place and you make an application. Not an application - you write an email.
"The parties involved are the player - very importantly - the club, Eddie Jones, PRL and the RPA. I think it's a really good process, actually.
"The decisions are taken in the best interests of the player and obviously we're delighted to have our players available."
Harlequins: Green; Marchant, Northmore, Anyanwu, Murley; Allan, Gjaltema; Marler, Head, Collier; Hammond, Herbst, Kenningham, Evans, Dombrandt.
Replacements: Walker, Kerrod, Louw, Lamb, White, Stafford, Edwards, Hyde.
Saracens: Daly; Malins, Lozowski, Tompkins, Lewington; Farrell, Van Zyl; Mawi, Woolstencroft, Judge; Itoje, Tizard, McFarland, Earl, B Vunipola.
Replacements: George, M Vunipola, Clarey, Christie, Wray, Davies, Manu Vunipola, Taylor.
Referee: Tom Foley.