Momentary carried the Queen's colours to victory in the Swettenham Stud Fillies' Trial Stakes at Newbury.
QIPCO 1000 Guineas second Starscope was sent off favourite to further advertise the form of the Newmarket Classic but John Gosden's filly had to be walked down to post and also proved reluctant to load.
She did, however, jump out well and took the field along, racing a shade keenly in front for Jimmy Fortune, successful on Thursday in the Dante aboard another Epsom hopeful in Bonfire.
Momentary was produced to challenge by Hayley Turner inside the final quarter of a mile, getting first run on Darryll Holland aboard the well-backed Shirocco Star who could be seen travelling strongly.
The two fillies quickened well, racing head-to-head throughout the final furlong with Michael Bell's once-raced maiden prevailing by a short-head.
The pair pulled almost four lengths clear of Starscope who failed to pick up but, arguably, the biggest disappointment of the race was Fillies' Mile third Firdaws who never looked to be travelling and finished tailed off.
The Queen's winner may have been a big price, but it was not a major surprise for her trainer, who is now eyeing a trip to Royal Ascot.
Bell said: "I was hoping she'd run well as she'd been working like our best filly at home, but I wasn't sure how good that was if that makes sense.
"It's a nice surprise she's won as it looked a good race on paper, but I was hoping she'd give a good account of herself.
"It's nice to win any Listed race but it's obviously particularly satisfying to win for Her Majesty.
"This filly isn't entered in the Oaks and the plan is to go to the Ribblesdale Stakes at Royal Ascot.
"It will be nice for Her Majesty to go to Royal Ascot with a horse who hopefully has a good chance."
Last year's Oaks heroine Dancing Rain was beaten in this race last year and Sky Bet and Boylesports make Shirocco Star a 33-1 chance for the Investec Oaks while Paddy Power go 25s for the Epsom Classic.
Momentary's success was the second leg of a remarkable 1393-1 double for Turner after she guided Harry Dunlop's 40-1 shot Sir Patrick Moore to a debut victory in the Hildon Maiden Stakes.
Turner said: "I think this was Harry's first two-year-old runner (of the year), so obviously there was a bit of a question mark.
"He'd been going well at home, but it was a good Newbury maiden, as they always are.
"The horse knew his job really well and he won going away again at the end."