Irish Olympian Aoife Clark will win her first CCI three-star title if she showjumps clear at the Fidelity Blenheim Palace International Horse Trials in Oxfordshire on Sunday.
Clark, who finished seventh at London 2012, delivered a fine cross-country round aboard Fenyas Elegance to lead by 1.5 penalties from Frenchman Jean Teulere on Matelot du Val, while American Clark Montgomery lies third.
"She tried her heart out," said Clark, following her ride on the nine-year-old Irish-bred chestnut mare. "I just tried to ride the fences positively, and she's a super jumper, really powerful."
The Eric Winter-designed course proved influential, and only Gemma Tattersall, the highest-placed British rider in fourth place on Arctic Soul, achieved the optimum time of 10 minutes 10 seconds.
Bedfordshire-based Sarah Bullimore, leader after the dressage phase on Lilly Corinne, had a run-out at fence 21b, while Britain's world number two William Fox-Pitt fell from Before Time before retiring his second horse Running Order.
Fox-Pitt, though, leads the CIC three-star class for eight and nine-year-olds following a clear showjumping round on Fernhill Pimms, his current British Intermediate champion.
He was also in third place with Freddie Mac after a clear round, but was then eliminated for contravening a governing body rule on the style of hind-leg boots allowed in a young-horse championship.
"It is a real shame," Fox-Pitt said. "I think they (judges) have been quite mean.
"I was disqualified after my round, as was (Australian rider) Sam Griffiths. The sad thing is that once we had been pulled up on it, they checked everyone else's boots before they went in."