Aidan O’Brien is set to rely on French Guineas heroine Diamond Necklace as he bids for a second victory in the Prix de Diane Longines at Chantilly on Sunday, with stablemate Moments Of Joy also under consideration for the €1 million Classic. The Ballydoyle trainer, whose sole success in the race came with Joan of Arc in 2021, believes both fillies have profiles suited to the 2,100-metre contest, one of the most prestigious prizes available to three-year-old fillies.

Diamond Necklace arrives at Chantilly off the back of her victory in the French Guineas, and O’Brien reported that the filly has continued to thrive since that performance.

Reflecting on her preparation, O’Brien said the Diane had always been the intended target if all went well in the Guineas. He noted that everything had gone according to plan since her latest victory and added that he believes she is even more effective on better ground.

“The plan was always, if everything went well in the Guineas, to come back here,” O’Brien said. “Everything has been very good since her last victory. I think she’s even better on better ground.”

Significantly, O’Brien indicated that stamina has never been a major concern despite the step up in trip.

“We always thought a mile and a quarter shouldn't be a problem to her,” he said. “She’s good, very straightforward. She’s well balanced. She’s a medium-sized filly and usually travels well in her races.”

The trainer also drew comparisons with her sire, St. Mark’s Basilica, who improved when stretched out in distance during his own racing career.

“She’s very like her sire St. Mark’s Basilica,” O’Brien said. “When he went up to a mile and a quarter, he improved again and everything she does is very like him.”

While the Diane often brings together fillies with differing racing styles, O’Brien played down the importance of race tactics, stressing that a truly run contest usually reveals the strongest horse.

“All we ever want is an evenly run race and then everybody finds out where they stand afterwards and whether their horse gets the trip or doesn't get the trip,” he said.

Looking beyond Sunday, O’Brien did not rule out Diamond Necklace eventually tackling 12 furlongs.

“It definitely is possible,” he said. “Especially being by St. Mark’s and on her dam side as well.”

Moments Of Joy Remains Under Consideration

Moments Of Joy has yet to be confirmed for the Diane but remains firmly in contention after her latest appearance in the Musidora Stakes at York, a recognized Oaks trial.

O’Brien felt the race circumstances were not ideal but believes the filly retains considerable upside.

“It went a little bit steady for her, but she ran okay,” he said. “We think there’s more improvement to come from her, and we think she'd like the trip, and we think she'd like the track as well.”

The trainer also suggested that quicker conditions would be in her favor.

“I think she'd like light and nice ground,” he said. “I don't think she'd be mad about soft ground. She's a very good mover.”

Preparation Extends Beyond The Stable

One of the notable features of O’Brien’s race preparation is his practice of walking major racecourses alongside his jockeys. He explained that the process is designed to prepare for as many race-day scenarios as possible while identifying the best available ground.

“We go through every furlong,” he said. “We go on the grass on the track and try to prepare as well as we can, really, for all different kinds of scenarios. We speak and talk and communicate a lot as we go along.”

According to O’Brien, the exercise is as much about communication and planning as it is about studying the physical characteristics of the track.

A Record Of Success At The Highest Level

Now in his 34th season as a trainer, O’Brien remains one of the most successful figures in modern Flat racing. Since taking over at Ballydoyle in 1996 as trainer for the Coolmore operation, he has amassed nearly 450 Group 1 victories across nine countries, four continents and both hemispheres, while collecting 28 Irish Champion Flat Trainer titles.

Despite that extraordinary record, the Prix de Diane has proved difficult to conquer. His lone success came with Joan of Arc in 2021, a daughter of the influential broodmare You'resothrilling. That mare has produced four Diane runners for the stable, including Joan of Arc, Happily, Coolmore and Toy.

On Sunday, Diamond Necklace will attempt to give O’Brien a second victory in the Chantilly Classic, while Moments Of Joy could yet provide the Ballydoyle team with another strong hand in one of Europe's most important races for three-year-old fillies.