"Since we dropped her back to five furlongs she's just improved and taken a step up.
"She was very green in her younger days and we tried to stretch her out in trip, but bringing her back to five (furlongs) has been the making of her.
"It will be the King's Stand next, along with Profitable.
"Alan (Spence, owner and Chelsea director) is obviously at the Cup Final but I'm delighted to win this for him again as he's been a huge supporter.
"She's making up into a really strong filly and it's uncanny to win the same race again."
The four-year-old filly got off to a decent start and tracked the pacesetting veteran Take Cover for much of the five-furlong contest.
Priceless hit the front over a furlong out and while Goldream finished powerfully, Cox's charge held on by half a length.
Alpha Delphini was a close-up third.
Kirby said: "She's very good and I was riding the best filly in the race."
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