With only two behind him with three furlongs to run, the son of 2011 Derby victor Pour Moi came from the clouds as O'Brien won the Classic for the sixth time. On Friday, bookmakers were even betting on betting; which colt, most likely Cracksman or Cliffs of Moher, would go off favourite?
Joseph O'Brien rode two Epsom Derby winners and on Saturday he could become only the second person to also train a victor of the great race, in so doing denying his father Aidan.
"I had a great feeling going down", said Beggy, "I probably pulled a little hard, but I got there at just the right time".
Douglas Macarthur and The Anvil made the early running, opening a six to seven length lead as they climbed the hill in the first half of the course.
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Cliffs Of Moher was second and Cracksman third.
Cracksman - the 7-2 favourite - was never too far away under Frankie Dettori for John Gosden, and did well to stay on like he did.
Beggy added: "A furlong down I thought if I get a run I'd win, I knew Ryan had gone, but in fairness to the big horse his best furlong is his last, which makes a big difference". It would also be a big day for the stallion Frankel and his reputation would go up even higher thanks to the win.
However, he has made giant strides forward since, with his narrow defeat to Cracksman at this track in April followed by a dominant win at Newmarket and victory in the Dante Stakes, which has always been considered Britain's best Derby trial. "We're very lucky to have him". He told ITV Sport: "What can I say he is a world-class rider, he is tactically very aware".
O'Brien went on: "Ryan's horse got there and just got exhausted, but Padraig gave the victor a great ride".
"We were anxious Cliffs Of Moher just came to hand late, it was a rush to get him to Chester, we had to have a run, if he hadn't he wouldn't have been here".