Thunder, lightning and driving rain have added to the drama as Enable upset odds-on favourite Rhododendron in the Oaks at Epsom.

Frankie Dettori claimed his fourth win in the Classic when he steered the John Gosden-trained Enable to a five-length victory on Friday (Saturday AEST).

Rhododendron was among a plane load of Aidan O'Brien-trained horses to arrive just in time for the races after technical difficulties in Ireland.

Before the Oaks, American challenger Daddys Lil Darling bolted to the start, with Olivier Peslier deciding to bail out just before she reached the stalls.

"She pulled away in the last furlong and is a good mare," Dettori said.

"In the back of my mind I thought we had a chance. The rain spoiled it a bit as I was concentrating on my game plan so I didn't have much time to celebrate crossing the line."

Gosden said the Irish Oaks was the likely next start for Khalid Abdullah's filly.

"I see no point in going back in trip with Enable now," he said.

"There's some lovely races, like the Irish Oaks."

O'Brien had better luck with Highland Reel who proved a class above to stretch his Group One tally to five in the Coronation Cup.

The 9-4 favourite dominated from the front under Ryan Moore and comfortably held the Godolphin-owned pair of Frontiersman and Hawkbill at bay.

"What happened this morning was unavoidable. The lads were doing their best but things weren't running smoothly," O'Brien said.

"It's a big team effort and I'm thankful to them all for making it happen.

"I'm delighted with him (Highland Reel). He's obviously gone through a lot today.

"He's an amazing horse this. He's tough, he has tactical speed and he stays.

"He has the option of the Hardwicke at Royal Ascot and then on to the King George."

The much-travelled Highland Reel finished third to Winx in the 2015 Cox Plate before winning the Hong Kong Vase and last year took out the Breeders' Cup Turf at Santa Anita.