Hilary Mantel is Booker favourite

A month before the Man Booker Prize shortlist is announced, Hilary Mantel, one of 13 authors named on the longlist released last week, has shot into the lead as a clear public favourite to win the prize with her novel Wolf Hall, a retelling of the life of Henry VIII's hated chief minister Thomas Cromwell.

No one is sure how it has happened, least of all the bookmakers who, given the level of early betting, have reduced the odds from 12-1 to 2-1 in a matter of days. William Hill said it had "never seen a betting pattern like it".

A spokesman told the Guardian: "We'll lose a five-figure sum if the support continues. It is as though a tip has gone around the literary world telling everyone that Mantel is a certainty."

This is highly unlikely given that the judges, chaired this year by BBC Today show presenter James Naughtie, have yet to discuss a shortlist.

The best explanation, according to the Guardian, is a flurry of betting on Saturday following BBC TV's Newsnight Review on Friday, where the book received a very warm reception.

Biographer and historian Kate Williams said: "The evocation of both the high court and lowlife of London was spectacular... This representation of Cromwell's inner life and the way in which we see a completely different vision of [Sir Thomas] More is fantastic." In short, she said it was a "fantastic" book.

The worry for Mantel (pictured receiving her CBE in 2006) is that the undue attention could backfire on her, with Naughtie and his judges anxious to prove the winner is not a foregone conclusion when they meet in early September to whittle the 13 down to six. The winner will be announced a month later, on October 6. ·