Victoria Pendleton was unseated on her first ride over regulation fences in the Betfair Switching Saddles "Grassroots" Fox Hunters' Chase at Fakenham.
The dual Olympic champion cyclist was riding the nine-year-old Pacha Du Polder for a second time, with the pair having been beaten in a photo-finish at Milborne St Andrew point-to-point in late January.
The Paul Nicholls-trained gelding was the 8-13 favourite for this three-mile contest and Pendleton gave her mount time to find his feet, initially dropping him out at the rear of the six-runner field.
Pacha Du Polder gradually warmed to his task and was moving closer to the leaders when he was slightly impeded by Baltic Blue at the seventh fence.
Pendleton and Baltic Blue's rider Carey Williamson crashed to the ground, but both riders were soon on their feet.
The race was won by Vasco Du Mee.
Hit ❤️ if you'll have one eye on Victoria Pendleton's first ride under rules. pic.twitter.com/NfLQmegHmJ— bet365 (@bet365) February 19, 2016
Pendleton announced last March that she was embarking on the Betfair-backed 'Switching Saddles' challenge to make the transition from velodrome to racecourse, with the ultimate aim of riding at the Cheltenham Festival.
After four months of intensive training with racehorse trainer Lawney Hill, eventing guru Yogi Breisner and former event rider Chris King, Pendleton gained valuable racecourse experience in charity events and, later, in amateur riders' races on the Flat.
She came close to making a dream debut under Rules after finishing second, beaten just a head, aboard Royal Etiquette on her first ride as a fully-fledged amateur at Ripon in August.
She turned her attentions to the jumping game in the autumn, riding in several point-to-points before making her debut under National Hunt Rules at Fakenham.
Pacha Du Polder, who carries the colours of leading owners the Stewart family and finished second over the Grand National fences in the Fox Hunters' Chase at Aintree last term, had already been earmarked as Pendleton's intended Festival ride in the St James's Place Foxhunter Chase on March 18.