The 33-1 outsider Cercene triumphed in thrilling finish to become the longest-priced winner of the Coronation Stakes at Royal Ascot.
Winning jockey Gary Carroll was headed by the French-trained favourite Zarigana but his mount fought back to win by half a length, with January in third.
"It's a lifetime's ambition to have a Group One winner. It's 50 years of work," said victorious Irish trainer Joe Murphy, who was only having his second runner at the Royal meeting.
Cercene went off at big odds despite finishing a good third in the Irish 1,000 Guineas.
"It's unbelievable. She's very tough, she wanted to win. To do this at Royal Ascot is magic," said Carroll.
Friday's other top-level Group One contest saw another surprise winner as 25-1 chance Time For Sandals landed the Commonwealth Cup as favourite Shadow Of Light could only finish fifth.
Richard Kingscote rode the victor, who is nicknamed 'Flip Flop' at her stables, from stall one for in-form trainer Harry Eustace.
Eustace was celebrating a top-level Group One double, having won Tuesday's opening Queen Anne Stakes with Docklands.
"It's the hardest place on earth, but the horses have turned up in great shape," said Eustace.
Shadow Of Light was last year's champion juvenile and had finished third in the 2,000 Guineas behind his victorious stablemate Ruling Court, but trainer Charlie Appleby said he was unsuited by the good to firm going.
Venetian Sun, trained by Karl Burke, won the Albany Stakes to end Aidan O'Brien's stranglehold on this week's juvenile races.
Horses drawn high had fared well on Thursday but the 7-1 victor also broke from stall one on Friday under Clifford Lee and comfortably saw off his rivals, with O'Brien's favourite Signora back in ninth place.
"I think she's very special, the best two-year-old filly I've trained," said Burke.
Venetian Sun is part-owned by Brighton and Hove Albion supremo Tony Bloom, who hopes she will be a contender in next year's 1,000 Guineas.
Ethical Diamond, trained by Willie Mullins, gave Ryan Moore a sixth winner of the week in the Duke Of Edinburgh Stakes.
The 3-1 favourite was an unlucky fourth in the race last year but made no mistake this time.
It was a poignant win as Ethical Diamond's sire Awtaad was trained by Kevin Prendergast, who died aged 92 earlier on Friday.