London (AFP) - Japanese contender Deirdre sprang a 20-1 surprise in the Group One Nassau Stakes at Glorious Goodwood on Thursday to foil the all conquering John Gosden and Frankie Dettori.
Dettori and trainer Gosden had notched up their ninth top grade success in two months 24 hours earlier with Too Darn Hot in the Sussex Stakes.
And the pair had high hopes for Mehdaayih, sent off at 3-1 second favourite behind Aidan O'Brien's Hermosa.
With O'Brien's Irish Oaks winner folding tamely it was Deirdre under Oisin Murphy who stole the show, coming from way off the pace to defeat Dettori on Mehdaayih by a length and a half.
"That felt unbelievable," Murphy told Britain's ITV.
"This is a dream come true, a massive day for Japan and I'm delighted to have done the steering. I'm thrilled," the winning jockey added.
Deirdre, undone by soft ground at Royal Ascot in June, is trained by Mitsuru Hashida and has been based at a stable in Newmarket for the summer.
The five-year-old mare was emulating her sire, Harbinger, who won at the Goodwood festival 10 years ago.
Her success will add impetus to Japan's long and frustrating quest to land the Prix de l'Arc de Triomphe, run at Longchamp in France in October.
Thursday's win comes two days after Japan's champion racehorse and leading stallion Deep Impact was put down.
Deep Impact placed third in the 2006 Arc, only to be subsequently disqualified for failing a drugs test.