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The 11-4 favourite, ridden by Ryan Moore, was in front after a furlong and stayed there without ever having to come under strong pressure.
Joan Of Arc was restating her case for a clutch of high-profile entries in top races over the coming months, having failed to build on her Curragh maiden victory when only sixth in a similar trial over seven furlongs here last month.
Up to a mile in this Group Three, the daughter of Galileo – a full-sister to Classic winners Gleneagles and Marvellous – always appeared in control and had a length and three-quarters in hand at the line.
Her nearest pursuer was 50-1 shot Flirting Bridge, with the same distance back to another outsider Thinking Of You (40-1) in third.
Paddy Power reacted by halving Joan Of Arc’s odds for both Royal Ascot’s Coronation Stakes (into 8-1) and the Cazoo Oaks at Epsom (into 10-1) next month.
O’Brien said: “The last day was a bit of a non-event for her, but she came out of it lovely.
Earlier, Maker Of Kings returned to winning form in first-time blinkers with an authoritative display in the Amethyst Stakes.
Ger Lyons’ four-year-old was runner-up in the Irish Lincolnshire on his first start this season and was then a beaten odds-on favourite when he went down by a short head at Tipperary last month.
But he had no trouble with this rise in class to Group Three level, as the 7-1 winner under Colin Keane.
Maker Of Kings was soon up with the pace set by Raise You, then took over in the final two furlongs to assert by a length and a quarter – with Erzindjan staying on to get closest to him, a neck in front of 7-4 favourite Ace Aussie.
Lyons’ assistant and brother Shane said: “He’s a grand horse who ran well in the Lincoln. Colin said we should put headgear on, and it’s worked.
“He’s a fun horse for his owners. He loved the ground and will get further.
“We’ll probably put the headgear on and off. He just gets a bit lonely – and with the headwind today, it helped.”
Eaglefield gave trainer Jim Bolger and jockey Kevin Manning a winning start on the card as he got off the mark at the second attempt in the opening John R Fitzpatrick Agricultural Contractor Maiden.
The Gleneagles gelding was second on his Gowran debut over this same trip of seven furlongs just four days ago.
He proved he was ready to go again, though, sitting just behind Jeroboam and clear of the rest before collaring the long-time leader in the final furlong and then just having enough left to hold on from closers Baldomero and Emilie Gray by a neck and a head.
The line came just in time for the 13-8 favourite, for whom there do not appear to be any big plans just yet.
Bolger’s daughter Una Manning said: “You’d be happy with him – Kevin said they went a right gallop the whole way, and he battled well.
“I’m told we’ll see how the handicapper treats him and go from there. The plan was to come back here, and then maybe go to the Irish Guineas.
“Ryan said she might stay a bit further so we’re very happy with that. She’s a very relaxed filly.”Watch every race from the 2021 Dante Festival (May 12 - May 14) at York on Racing TV!
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