The former dual champion jockey only took out his training licence earlier this year, following in the footsteps of his father Aidan O’Brien – who completed the Derby and Oaks double at Epsom on Saturday – and his brother, Joseph.
O'Brien Jr, 21, was not present. He watched the race in the stands at Fairyhouse, where he also had runners. It was only the fourth victory of his fledgling career.
Fancy Blue was a 13-2 shot to provide the fledgling handler with a first Classic success in the French Oaks, having filled the runner-up spot behind O’Brien senior’s Peaceful in the Irish 1,000 Guineas three weeks ago.
The pair renewed rivalry in France – and were joined on the trip from Ireland by the Jessica Harrington-trained Alpine Star, who was the 6-4 favourite to follow up her triumph in the Coronation Stakes at Royal Ascot.
Drawn one, the latter made much of the running in the hands of Stephane Pasquier and did not go down without a fight, but Fancy Blue eventually wore her down under Pierre-Charles Boudot to claim a narrow victory.
Peaceful was just behind her compatriots in third.
"It's nice to get a big one on the board," O'Brien told Racing TV, with some understatement, at Fairyhouse.
"I thought she had a very good chance - she was obviously every eye-catching in the Irish Guineas - and that the step up in trip would suit. I was hopeful of a big run and Pierre gave her a fantastic ride. I'm delighted."
He added: "I've got a fantastic team of lads at home - I'm as delighted for them as much as anything else.
"We will take a look at the Nassau or the Irish Oaks. We will make a plan when she gets home."Get your free Racing TV fleece - the latest in our range of high-class Racing TV merchandise! Click here for more details.
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