Joviality edged out Barefoot Lady to win the Musidora Stakes at York after a photo finish.
The Cape Cross filly, trained by John Gosden, prevailed by a head from the Richard Fahey-trained second.
Amazing Beauty, for Aidan O'Brien, and Henry Cecil's Arizona Jewel were left trailing the leading pair.
Gosden said the extended one and a quarter mile trip was stretching the stamina of the 5-1 winner, ridden by William Buick.
The trainer ruled out a tilt at the Epsom Oaks on 3 June, preferring the Prix de Diane [French Oaks] at Chantilly nine days later.
"We are clear in our mind that a mile and a quarter is the top end of her range," said the Newmarket trainer.
"She's in the French Oaks and that's where we'll go."
Jovality was second at Sandown on her previous run, whereas Barefoot Lady was fifth in the 1,000 Guineas having won the Nell Gwynn Stakes at Newmarket.
Sandown maiden winner Arizona Jewel was sent off the 11-8 favourite as Cecil sought his 10th Musidora win.
But while travelling better than anything turning into the straight, she was unable to pick up when it mattered.
Irish raider Amazing Beauty made the early running, but she faded tamely.