Certify showed an impressive turn of foot to take her 100% record to four in the Shadwell Fillies' Mile at Newmarket.
Held up at the back of the field in the early stages by Mickael Barzalona, the 4-6 shot was asked for an effort and picked up in a matter of strides to go from last to first just over two furlongs out.
Mahmood Al Zarooni's charge was soon well clear and went on to score by four and a half lengths from Roz, with Amazonas third as Godolphin took this Group One prize for the third year running.
Al Zarooni said: She's done very well. She was a bit excited before the race which is not normal. Maybe a faster pace would have helped.
"I think we'd prefer to put her away for next season now. She's a lady and we should look after her.
"I can't say for 100% if she's better than Lyric Of Light (won Fillies' Mile last year) but she has won by four lengths and I think the other one only won by a head."
Simon Crisford, Godolphin's racing manager, said: "She's a top notch filly but it's a shame John Gosden's filly (Winsili) didn't run as we might have had a better idea where we stand."
Barzalona said: "When you have good horses it is easier.
"She's a very nice filly, she's improved with each race and I hope she keeps going.
"Today is the first time she has won well, when I asked her to go she answered.
"She's very straightforward and she kept going. She looks exciting for next year and should be good."
Harry Dunlop said of Roz: "I'm absolutely delighted and I think the winner is a very good filly. Jim Crowley said they didn't go a great gallop but you can't complain as she's been second in a Group One. I suspect we'll finish her for the season now."