It was the first Classic victory for Haggas and his stricken wife Maureen, once married to legendary jockey Lester Piggott, since their Newmarket stable won the 1996 Derby with Shaamit.
The unfancied filly – the beneficiary of an inspired piece of front-running by Johnny Murtagh – held off the late, and sustained, challenge of the strongly-fancied Wonder Of Wonders, the mount of Kieren Fallon, to prevail by three-quarters-of-a length.
As Dancing Rain, a 20-1 shot, was led into the winner’s enclosure, Mrs Haggas was happy to forgive the Oaks heroine – even though her own leg was in plaster following the accident earlier this week during a starting stalls test.
She said: “It was just one of those silly accidents, It wasn’t her fault, but unfortunately I broke my fibula so having ridden her all winter, I haven’t been able to ride her all week.
“It’s been extremely frustrating, but one of the other girls in the yard, Rosie, has ridden and she has done a brilliant job.”
Murtagh, who rides Native Khan in today’s Derby, was winning the Oaks for the first time. He only decided on these inspired tactics after watching Dancing Rain’s past races.
“I spoke to William and I said ‘I think I’ll make the running’. I watched the videos and she seems to travel very well and is uncomplicated,” he explained.
“We were able to set a nice pace but she was ducking and diving, so I knew there was loads left in the tank.”
In a slowly-run affair, those who were ridden with restraint failed to get involved. The previously unbeaten Zain Al Boldan did her chances no favours by failing to settle, while the Sir Michael Stoute-trained Havant, sixth in the 1000 Guineas, was never nearer than 10th.
Blue Bunting, the 9-4 favourite, was settled in the middle of the pack for much of the contest, but failed to pick up sufficiently to trouble the leaders.
Her jockey Dettori was later banned for 10 days for dropping his hands – and allowing William Buick’s mount Izzi Top to pass his mount in the final furlong to finish third at 25-1.
Unless any appeal made is successful, Dettori will be absent from June 17-26 which means he will miss the final two days of Royal Ascot, most notably the ride on Delegator in the Golden Jubilee Stakes.
He will also sit out the following week, including the Irish Derby meeting.
Having blamed Blue Bunting’s disappointing performance on the slow pace and undulating track, Dettori left Epsom without making further comment.
Earlier Aidan O’Brien’s St Nicholas Abbey returned to pre-eminence by outbattling Midday to land the Coronation Cup under Ryan Moore.