The Andre Fabre-trained French raider had finished a modest six-lengths fifth behind stablemate Intrepidity in the Energizer Oaks Oaks at Epsom last month, but emphatically turned the tables this time. Intrepidity finished only fourth, a short-head behind third- placed Oakmead.
Royal Ballerina's stable companion, Flame Of Persia, set a strong pace in the early stages, tracked by Lester Piggott on Danse Royale, with Royal Ballerina and Oakmead, Intrepedity and Wemyss Bight all held up.
Turning for home, about four furlongs out, Piggott sent Danse Royale into the lead and, momentarily, the pair appeared to be going best. This was more than could be said of Intrepidity, whose jockey, Michael Roberts, had to work hard just to reach a challenging position. She struggled home for a minor placing.
Danse Royale surrendered the lead two furlongs out but there was still hope for the Irish as Willie Supple, deputising for the injured Warren O'Connor, went on aboard Royal Ballerina. This filly had run the bravest of races when three-quarters of a length second to Intrepidity at Epsom and looked set for compensation.
However, one look at Eddery, sitting in Royal Ballerina's shadow with his mount, Wemyss Bight, on a tight rein, confirmed that the game was up.
When Eddery asked Wemyss Bight to quicken in the last 200 yards, the Khalid Abdullah-owned filly went almost a length up and, though Royal Ballerina rallied a little close home, the telling blow had already been dealt.
'I was told to hold up Wemyss Bight for a late run. At Epsom she didn't pick up at all in the straight, but I was confident that her form overall was equal to that of the favourite,' said Eddery afterwards.
'This time Intrepidity had an off day and my filly left her English Oaks form behind,' he added.
Michael Roberts explained that Intrepidity was already struggling at the top of the hill.
'She seemed OK until the pace quickened and she never got hold of her bridle. Maybe Epsom took more out of her than we had thought,' he said.
Fabre, saddling his first winner in Ireland, intends preparing Intrepidity for an autumn campaign at Longchamp, centring on the Prix Vermeille and the Prix de L'Arc de Triomphe.