Mounting tension at the William Hill Sports Book-of-the-year award was quickly deflated yesterday when one of the shortlisted authors inadvertently announced the winner ahead of time.

Paul Kimmage, accepting a bound copy of his book Full Time at the award ceremony, let slip that the £12,000 prize had been awarded to Laura Hillenbrand's Seabiscuit.

Hillenbrand is the first female winner of the prize, which publishers have said can double a book's sales.

Seabiscuit is a rags-to-riches biography of a racehorse in America during the Great Depression, and may follow in the footsteps of previous winner Fever Pitch by making it onto the silver screen.

"It wasn't ideal," said John Gaustad, the chairman of the panel of judges. "It sort of reduced the tension, but I'm sure it was an honest mistake."

Kimmage, who writes for the Sunday Independent, stepped off the podium to mumblings from the assembled crowd, and quickly buried his head in his book Full Time, the story of Tony Cascarino's life as a footballer.

The prize ceremony, described by Gaustad as 'quite a hot ticket', is not a stranger to controversy. Previously, audiences have been treated to fits of rage from disappointed authors.

Once, a judge was even pushed into a corner and harangued by an author, while another time a shortlisted writer shouted an obscenity and stormed out.