Organisers cancelled this year's Badminton Horse Trials, arguably the world most prestigious annual three-day event, saying Monday there was "no chance" of the ground drying in time for that would have been a key part of many riders' Olympic preparations.
The competition, which takes place in the grounds of Badminton House in Gloucestershire, south-west England, was due to start on Friday.
As well as the upcoming London Olympics Games, this year's Badminton had been given added significance by the fact Britain's world number one William Fox-Pitt was gunning for the Â£220,000 ($358,000) Rolex Grand Slam prize awarded for any rider who wins consecutive Burghley, Kentucky and Badminton titles.
Fox-Pitt added the Kentucky title on Sunday to his Burghley victory seven months ago, both aboard Parklane Hawk.
But his chance of a clean sweep has now been dashed.
"The recent exceptional rainfall has left the ground at Badminton totally waterlogged and partially flooded," Badminton director Hugh Thomas said Monday.
"Further rain is due this week, leaving no chance of the ground drying out.
"Very sadly, therefore, the 2012 Mitsubishi Motors Badminton Horse Trials has been cancelled."
The event will not be rescheduled, with Monday's announcement the first Badminton cancellation since 1987. The event was also called off in 1963, 1966 and 1975.