For the first time in its history the organisers of the Devon County Show have had to cancel the event after a pedestrian was involved in a collision.
The three-day event near Exeter was halted after the accident, involving five vehicles and a pedestrian, happened at around 2.05pm in a car park by the Westpoint showground's Blue Gate.
There have been huge tailbacks and delays all afternoon because of the closure of the car parks.
Show secretary Ollie Allen said: "Quite exceptionally heavy rainfall before and during the show have turned the car parks in quagmires."
The pedestrian, thought to be a man in his 70s, was taken to the Royal Devon and Exeter Hospital with what police initially said were serious injuries, but they turned out not to be so.
One male driver sustained facial injuries in the collision and was also taken to hospital and one other person was described as walking wounded.
Two horseboxes were damaged, leaving two animals trapped. One horse had to be sedated while it was rescued, police said.
Organisers said their immediate concern was to get everyone safely off site on Friday when the show closes at 18:30.
In a statement issued this afternoon Devon County Show secretary Ollie Allen said it was a “heartbreaking” decision and blamed “exceptionally” heavy rainfall turning the car parks into quagmires.
It promised that lessons would be learnt and that the board would meet later to discuss the financial implications.
“We are very sorry to have to announce that for the first time in our history that we have been forced to cancel the third day of the Show tomorrow (Saturday) in the interests of public safety,” she said in the statement.
“Quite exceptionally heavy rainfall immediately before and during the show has turned the car parks into quagmires to the point where it would not be safe to allow people to park their cars.
“The board of the DCAA will be meeting in due course to consider all implications of this decision including the financial implications. Further announcements will be made in due course.
“It is heart breaking to have to make this decision but the appalling weather has left us with no choice. We are not the first agricultural show to have to cancel a day’s activities and we won’t be the last.
“We will be considering the long term implications of this and the lessons that need to be learnt in due course. For the moment our thoughts are with our visitors, exhibitors, trade stand holders, sponsors and our army of volunteers for whom this will come as a bitter disappointment.
“We did everything we could to improve the state of the fields but in the end the intensity of the rainfall was too much.”