Emma Johnathan, 23, fell at fence 19 and was pronounced dead at the scene. Emma, from Petersfield, Hampshire, was riding her own horse, El Nino, a nine-year-old mare, in the two-star class at Hartpury. She had ridden El Nino at two star events at Barbury and Longleat earlier this year.

Hartpury Horse Trials organisers were not releasing any details of the accident, but it was reported in The Times that fence judges could not identify the cause of the accident, and that Emma had been riding well.

On the Horse and Hound website yesterday, a fence judge said: "Emma rode beautifully and did absolutely nothing wrong. It was one of the best approaches to the fence that we had seen. It was just a tragic and very unfortunate bit of bad luck."

The cross-country court at Hartpury was designed by Olympic designer Mike Etherington-Smith in 2007, and has been described as "challenging". In a pre-event statement, organisers said the event's new cross-country course designer, Eric Winter, had made very few changes to the 2007 course, which had remained untested due to the floods that hit Gloucestershire last summer.

Alex Fox, Chairman of British Eventing said: "On behalf of the whole sport, I would like to extend our deepest sympathy to Emma's family. The thoughts and prayers of eventing people all over the UK are with them at this sad time."

In a statement, Hartpury College, the organisers of The Mitsubishi Motors Hartpury Horse Trials, Mitsubishi Motors and all those associated with the event, extended their deepest sympathy to Emma's family and friends.