Frankie Dettori’s 21st British Classic winner was the easiest yet, as the 11-2 chance Snowfall strode 16 lengths clear of her field in the Oaks here on Friday, the biggest winning margin in the race’s 242-year history. The result also means that both Snowfall and Mother Earth, who famously ran under each other’s names in the Group One Fillies’ Mile at Newmarket last October, have gone on to win Classics under Dettori this year. Persistent rain which changed the going to good-to-soft by mid-afternoon may have exaggerated Snowfall’s superiority slightly. However, this was still an astonishing performance by Aidan O’Brien’s filly and as a result her price for the Prix de l’Arc de Triomphe in October was cut from 33-1 to just 5-1. Dettori was happy to sit towards the back of the field in the early stages, with Santa Barbara, the favourite and O’Brien’s apparent first-string, one of the few fillies behind him. He made smooth and rapid headway towards the lead after rounding Tattenham Corner, moved alongside the longtime leader, Mystery Angel, a furlong out, and then unleashed the explosive finishing kick which carried Snowfall further clear of her field all the way to the line. The 16-length winning margin added four lengths to the previous record, set by Sun Princess in 1983, while O’Brien has now won the Oaks nine times and moved to 40 wins in English Classics. “I’ve won many Classics but not one as easy as that,” Dettori said. “It was unbelievable. I wanted a better position but they were going way too fast. Everybody was fighting to get in the first three so I let them get on with it. “I thought out there I had everything beat. In front they had all gone and I had the luxury to take one set of my goggles down. I thought, ‘don’t be clever, just cut through the middle’, and I did. “The only horse I hadn’t seen yet was Santa Barbara and I had a quick glance and I was already five in front. [Then] she took off, as simple as that. I knew I was at least eight in front [at the line]. “It is quite remarkable because I pulled up by the stables and everyone pulled up by the winning post. I was watching a documentary on the great Fred Archer yesterday and I’ve equalled his record of 21 [Classic wins) so I’m now only nine behind Lester [Piggott].” Now into his sixth decade, Dettori is concentrating ever more on quality rather than quantity, and this was just his seventh success in the jockeys’ title race, which started in early May. His wins, however, include two Classics, the Chester Cup and a Group Three, and he will set off at around 8-1 to win a third Derby at Epsom on Saturday on John Leeper. Snowfall started her three-year-old campaign with a solitary win in a maiden event to show for seven outings as a juvenile, but O’Brien insisted after Friday’s success that she had always been seen as a potential Group One winner at home. “We thought she was a proper Group One filly last year,” he said. “Usually, if they show that kind of class, it will come. “She ran in the Fillies Mile at Newmarket, those were the kind of races she was running in, but maybe she got stronger over the winter. “Ryan [Moore] said [Santa Barbara] cantered into the race, and he just said in that ground she just emptied out on him, so she’ll go back probably to a mile and a quarter.” Earlier on the card, William Muir’s Pyledriver fought off the persistent challenge of Al Aasy in the final furlong to register a first Group One success for his trainer in the Coronation Cup. “I started training in 1990 and I’ve never had a Group One winner,” Muir said, “but this is it and this is what we do it for.”