Zara Phillips has been withdrawn from Team GB for the Beijing 2008 Olympic Games following an injury to her horse Toytown sustained during training.
The injury to Toytown has not been revealed but as Phillips has no reserve horse, she has been forced to pull out.
"I am very disappointed not to have the opportunity to ride at the Olympic Games and feel that Toytown deserved his chance to go," said Phillips.
"However, with horses these things
happen and we have a very strong team."
The British Equestrian Federation (BEF) will nominate a replacement for Phillips and the British Olympic Association will make an announcement as soon as possible.
"The important thing to note is that Toytown has only a minor injury but it's enough to miss out on the Olympics"
"The choice now is whether to take a young rider with an experienced horse, such as Oliver Townend and Flint Curtis, or a more experienced rider with a younger horse in Tina Cook and Miners Frolic."
Phillips has a stable of horses but none of the same level as Toytown, whereas more established riders tend to have a better strength in depth.
Team GB 2008 chef de mission Simon Clegg, said: "This must be a huge disappointment to Zara particularly following the pair's success over the last few years.
"Naturally we now need to focus our full support on the rest of the team including Zara's replacement and give them every opportunity of competing to their full in Hong Kong."
Will Connell, team leader for the equestrian team, said: "The British team are saddened by the news, especially for Zara and her team.
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It is a double disappointment for Phillips after an injury to Toytown in 2004 forced her to miss out on the Athens Olympics as well.
She went on to win individual and team eventing gold at the European Eventing Championships the following year and was a surprise winner of the BBC Sports Personality of the Year in 2006 after winning gold at the World Equestrian Games.
And Connell explained: "We have to be realistic. Zara is the reigning World Champion and we had high hopes that she would help the team bring back a medal and also be in contention for an individual medal, so it is a blow.
"However we do have very good quality reserves and now it's up to the selectors to decide who they will recommend to the British Olympic Association.
"The important thing to note is that Toytown has only a minor injury but it's enough to miss out on the Olympics.
"The injury means that it would be unable to train day in and day out until the Olympics so it wouldn't be fair on the horse," he added.
"Zara is a fantastic team member and I hope we'll see her for London in 2012."
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