The novice chase at the Cumbrian course was disrupted when Brigadier Davis took a heavy fall at the third fence of the three-mile event and lay 15 yards from the landing side of the obstacle.
Course officials immediately put dolls and cones across the take-off side of the fence and a man waving a black and white flag ran on to the track when the seven remaining runners came round again.
The jockeys had no option but to pull up, although Judy Davies, on The Lighter Side, attempted to retrace her steps and jump the fence. She was unable to do so.
Mark Dwyer, who rode Squires Privilege in the race, said: 'There was no way the fence could be jumped. It was a bad fall and I was half expecting the dolls to be there when we came round again.'
Russ Garritty, rider of the ill-fated Brigadier Davis, was uninjured. The rules of racing make no provision for an obstacle being omitted once a race has started so all bets on the race are void.
Opening betting on Saturday's most important prize, the Champion Stakes, has Hatoof as evens favourite to emulate Triptych by winning successive runnings of the Newmarket race.
Muhtarram, Grand Lodge and La Confederation represent the best British hopes in an entry that also includes a second French challenger, Dernier Empereur, and two German horses, Lando and Embarcadero.
Hatoof has been in good form this term, coming to the race from an excellent victory in the Beverley D Stakes at Arlington in August.
Muhtarram is a 6-1 chance and will wear blinkers for the first time, having worked well in them at Newmarket on Saturday. But his owner, Hamdan Al Maktoum, could be double-handed if Mehthaaf takes her chance. The sheikh's racing manager, Angus Gold, said: 'We will have to see how she works before we decide, but she did not set the world alight at Ascot last time and I think it's unlikely she will run.'
CHAMPION STAKES (Newmarket, Saturday). William Hill: 11-8 Hatoof, 6-1 Muhtarram, 13-2 La Confederation, 7-1 Grand Lodge, 9-1 Dernier Empereur, 12-1 Mehthaaf and Turtle Island, 14-1 Alderbrook, Lando, 16-1 others. Ladbrokes: 11-10 Hatoof, 6-1 Grand Lodge and Muhtarram, 7-1 La Confederation, 8-1 Dernier Empereur, 14-1 Lando, Mehthaaf and Turtle Island, 16-1 Alderbrook and Sacrament, 33-1 others. Coral: evens Hatoof, 6-1 Muhtarram, 8-1 Dernier Empereur and Grand Lodge, 10-1 La Confederation, 12-1 Turtle Island, 16-1 Mehthaaf, 20-1 others.