Aidan O'Brien on Arc de Triomphe hopes Diamond Necklace, Minnie Hauk and Benvenuto Cellini

The Ballydoyle trainer has declared three runners for the 12-furlong ParisLongchamp showpiece, Diamond Necklace joined by three-year-old colt Benvenuto Cellini and last year’s narrow runner-up Minnie Hauk.

Diamond Necklace, a daughter of St Mark’s Basilica, appears the number one choice having won her first six starts including the French Guineas (1m) and French Oaks (1m2f), but was beaten for the first time in the Prix Jean et Louis Romanet at Deauville when last seen in August 23.

Explaining that relatively disappointing effort, O’Brien reiterated that his filly was not quite at concert-pitch on the day and bumped into a top-class winner.

“Obviously, we could have gone to the Vermeille and we said we wouldn’t, just in case she found it tough at that distance (1m4f) – and come Arc time she might have just been a little bit empty,” O'Brien told Sky Sports Racing.

“We decided to stay at a mile and a quarter and we got caught a little bit, we didn’t train her very hard for Deauville and the ground got bad and tacky.

“Obviously, Christopher (Head, trainer) had his filly (Aventure) in very good shape and we probably underestimated her a little bit and because of that the filly got beat. But she came out of that very well and she is in good form.

“It will be interesting – will she get a mile and a half? You can’t be sure until you see it. Her dad (St Mark’s Basilica) got a mile and a quarter well but obviously never went to a mile and a half, but there’s plenty of mile and a half in her family.

“There are plenty of things (you can analyse) like strength length and the way they relax, her heart profile… all those things suggest that she could (stay) but still you’re never sure until they do it.

“Then it’ll depend on how searching the pace is, whether it’s slow or whether it’s fast, so a lot of things will come into it. Until it happens, all you can do is hope really.”

Minnie Hauk hasn't quite hit the heights she did last year during the current campaign and while O'Brien isn't ruling out another big run on her return to the outskirts of Paris, he admits there isn't as much confidence in her as there was coming to the Arc as a three-year-old.

"We decided we would train her for the race this year although she has had plenty of problems with corns on her feet and we never really got a good run at her, probably in any race yet this year," he said.

"We were never going to over-train her anyway as she went through her preps. We were very happy with her run the last day, we decided to drop her in. We had a pacemaker in it and we thought the field would follow the pacemaker and we'd decided to take out time on her. Because the pace was so slow we just ended up back too far but she did come home well. Kalpana I think finished two or three lengths in front of her.

"We were very happy with the run and she's back where she was again. She wasn't beaten very far in it last year, obviously Francis' horse (Daryz) has had a good year - he got beaten but he's had a good year.

"She's obviously older so she is heavier and that would be understandable.

"Would you be as confident as last year? You couldn't say you would be because she has got beaten but we think there are loads of reasons why she did get beaten."

The chestnut Benvenuto Cellini has had a dramatic Classic campaign, winning the Chester Vase before being deemed a non-runner after finishing down the field in the Betfred Derby.

He bounced back to win the Irish Derby at the Curragh before running a good race in third behind Kalpana in the George, but seemingly has it all to prove again now after flopping as 2/5 favourite in last month's Prix Niel.

"He's in good shape," said O'Brien. "He ran in the Niel and we had a pacemaker in and we just didn't follow him which was probably to his detriment.

"He's a high-pace horse, a long-striding horse, and the pace got away so he was trapped back in the field and it was an ordinary pace.

"At that time our horses were running ordinary so all of them things put together maybe you'd think he could leave that run behind him.

"At the time, and three, four, five and six weeks before that, our horses were running well but they were all getting beaten and we found a little underlying, low-grade infection running through the place that we couldn't stop and was appearing out of nowhere.

"Two or three weeks ago we said that we would medicate everything, because we couldn't find where it was coming from or when it was going to come, so we did do that and ever since the horses have been running better. We think they are running better.

"He came out of the last race well. His work is very good, he's hardy, obviously you would like a nice bit of ground for him because he is such a nice mover.

"Really, we didn't think he would be running as we didn't think the ground would as nice as it's going to be, but his preparation went very well."

More on the 2026 Arc de Triomphe

• David Ord on Kalpana and the Juddmonte ties
• Ben Linfoot tackles the big Longchamp questions
• John Ingles backing title holder to double up
• Matt Brocklebank on the Longchamp undercard
• Simon Holt on why Maltese Cross is such an important runner
• Ian Ogg on the case for outsider Saddadd
• Nick Doggett recalls Fallon scoring on Hurricane Run
• For or against hot favourite Daryz?
• Who is the best bet in this year’s race?
• Tom Marquand feeling positive
• Colin Keane expects star mare to shine
• Arc de Triomphe preview podcast
• Arc odds from Sky Bet and Paddy Power