Top jockey Kieren Fallon was due to find out today whether he would be allowed to take part in this afternoon's Epsom Derby.
Two UK Court of Appeal judges were set to announce their decision at 9am on whether Fallon should be barred from the race.
Lord Justice Jackson and Lord Justice Elias were asked to overturn a decision made by a High Court judge yesterday.
Mr Justice MacDuff, sitting in London, refused to grant an injunction preventing the three-time Derby winner from riding in the classic event.
He had been urged to make the order by Ibrahim Araci, the owner of Native Khan, to prevent Fallon riding a rival horse, Recital.
Mr Araci brought his action over claims that Fallon had broken a "promise" to ride Native Khan and argued that, under the terms of a retainer agreement, he should not be allowed to ride any other horse in the race.
Fallon denied breach of contract and said there had been an "innocent misunderstanding".
Mr Justice MacDuff said he was satisfied "that the true facts are that the defendant (Fallon) believed he could ignore this binding contract".
In his judgment, the jockey had acted with "deliberate selfishness".
But, he said, in exercising his discretion on whether to grant an injunction, there were a number of factors to be put into the scale -- including the public interest.
He said he had "every sympathy" with Mr Araci, "who has been badly let down," but preventing Fallon from riding in "a premier classic race" would be "severe punishment indeed".
Although an injunction would cover "one short day", it would involve "a restraint of trade and a prohibition on a major sportsman from carrying on his occupation".
He added: "It is not just one day -- it is Derby Day."