The Aidan O’Brien-trained filly gamely made all in the hands of Seamie Heffernan and bravely repelled the challenge of Ryan Moore on the Qipco 1000 Guineas winner to claim the Group One spoils.
Two places behind Legatissimo when an unlucky fourth in the Investec Oaks, the 8-1 chance stepped forward in likeable fashion as she kept up the gallop in beating David Wachman’s runner by a short head.
The James Fanshawe-trained Ribbons was close behind in third under Frankie Dettori.
Diamondsandrubies, who had also impressed when winning the Cheshire Oaks, will now return to the Curragh for the Irish Oaks on July 18.
“She was very unlucky at Epsom and was probably the most inconvenienced by the whole thing (interference a furlongs and a half out). She was always going to come here and we said we’d let Qualify take her chance in the Derby,” said O’Brien.
“We’d like to have got a lead but that’s not the way it worked out, and Seamie gave her a great ride.
“We’ll ride her a bit more patiently over a mile and a half, and Qualify and Words will also run in the Irish Oaks.”
Heffernan said: “I was a bit unlucky at Epsom. Aidan trains them to progress from run to run and today she was at her best, so hopefully there will be more improvement.”
Bondi Beach (7-1) completed a quick big-race double for O’Brien and Heffernan with a gutsy victory in the At The Races Curragh Cup.
The winner and his stablemate Order Of St George both earned quotes for the Ladbrokes St Leger, with Paddy Power going 12-1 Bondi Beach and 14-1 Order Of St George.
Forgotten Rules was sent off the 8-13 favourite to gain compensation for his third place in the Ascot Gold Cup, but was only fourth after leading well into the straight.
O’Brien said: “They look two proper St Leger horses, and have pulled right away as well. The mile and six furlongs helped Bondi Beach and Seamie gave him a great ride.
“Order Of St George was entitled to get tired. He was ready in the spring and then got a temperature. He could go for something like the Voltigeur at York, while the winner may not need another run (before Doncaster).
“Seamie has been with us since the start. He’s a world-class rider and always was, and has been riding big-race winners for us for so long. He’s a massive part of the team and nobody deserves it (big-race double) more than him.”
Wachman and Moore enjoyed better luck with Most Beautiful in the Group Three Grangecon Stud Stakes.
Given a positive ride, the 11-8 favourite tracked the unbeaten Miss Elizabeth to the quarter-mile pole, before hitting the front with a furlong to run to beat Only Mine by three-quarters of a length.
Wachman said: “She’s always worked like a good filly. She’s big and is still a bit weak, you could see that in the last furlong. She has a nice future.
“She’s well entered up and will go further. The one thing is she likes goodish ground.”
RaceBets make the daughter of Canford Cliffs 20-1 from 25-1 for the Qipco 1000 Guineas.
Moore also struck on all-the-way winner Air Pilot (8-15 favourite) in the Hermitage Medical Clinic International Stakes.
Ralph Beckett’s six-year-old enjoyed an easy lead and had enough in the tank to shrug off Parish Hall by a length and a quarter.
“We were lucky to fall into a three runner Group Three. There’s not many of those around and we didn’t want to make the running as he’s lazy in front,” said Beckett.
“He’s ground dependent and needs juice in the ground. The rain last night was a big help. He was entitled to win a race of that nature.”
Foxy Forever (20-1) proved reluctant to go into the stalls but was a most willing parner in the race itself as Michael Wigham’s sprinter blitzed the opposition in the Tote Rockingham Handicap.
The five-year-old, blinkered for the first time, went through the front of the stalls which would have resulted in his withdrawal in England.
Thankfully for connections he was allowed to be reunited with jockey Colm O’Donoghue and went on to score by two and a quarter lengths.
Last into the gate, Foxy Forever got a flier from his stands side draw to win from two other British raiders, Discussiontofollow and Desert Law.
“This was on the agenda for a long time, and I knew he was a decent horse,” said Wigham.
“He’s a late-maturing type, just coming to hand. We wanted rain and we got it. He needs good ground or to get his toe in a bit.
“I thought he was too quiet beforehand in the parade ring and then he got too lit up at the start.
“Irish Champions Weekend could be on the cards. He won in the style of a good handicapper. We’ll take him home and see where we go. We’ll see what the handicapper does and then either stay in handicaps or go for stakes races.”
Sanus Per Aquam (7-1) got the better of Lieutenant General in a terrific tussle for the Barronstown Stud EBF (Colts & Geldings) Maiden.
Kevin Manning plugged away on Jim Bolger’s debutant to score by a length and a quarter.
Bolger said: “He could come back here for the Futurity and possibly the National Stakes after that.”