How did the judges reach their 2009 Man Booker shortlist? In some years the chair (man or woman) goes straight to a vote. This does not necessarily produce the six book shortlist, but it invariably separates the favourites from the also rans. In recent years two or even three books have emerged with judge-wide support and on a first vote have gone through. Then has come the debate for the remainder.

James Naughtie as this year's chair took a different approach. When the judges met at the Garrick Club with tea, coffee, water and biscuits as sustenance he asked each judge to sum up what they felt after a second reading of the books that formed the Man Booker Dozen, our thirteen-book longlist.

As Lucasta Miller, John Mullan, Michael Prodger and Sue Perkins (who came equipped with a variety of medicaments for battling against a virulent summer cold) talked of their rereading experience it became clear to me that this year perhaps four novels had widespread support - and by widespread I mean at least four of the five-judge team were in favour. In my time as literary director of the prize this is unprecedented.

A second reading of a novel shows up its strengths - and its weaknesses. One judge remarked how two of the thirteen book longlist went up in his estimation and two went down. Heads nodded round the table. Sue reached for a Kleenex. Another quickly acknowledged that the problem was not the titles that should go straight to the shortlist but the remaining two.

And so it proved when Naughtie decided to on a first vote. Ballot forms had been prepared. Each judge was asked to put an x against six titles they thought should go through. I had the fun, and the responsibility, of acting as teller and returning officer. The forms were anonymous, but it was clear immediately that the debate would, as one judge had suggested, be about which two would join the four titles so universally approved.

It has always been Man Booker practice not to reveal individual voting preferances. But let me say that in the end the debate was over three books of which only two could go through. My admiration for the judges rose; the standard of debate was high. It is easy to end up saying ‘I liked it', much tougher to explain why and give the precise qualities of an author's work. We are, after all, talking about the Man Booker here. From this shortlist on October 6 one novel will emerge supreme. Which one? Even if I were allowed to place my bet at this stage I'd be hardpressed to single out the eventual winner.

I shall join the judges and reread the shortlist. And so I hope will thousands of readers across the land.

Ion Trewin Literary Director