Hilary Mantel said she was left "weak at the knees" after becoming the first British writer to win the Man Booker Prize for Fiction twice after her novel Bring Up The Bodies was named the best book of the year.
The 60-year-old writer, who won in 2009 for the first part of her historical trilogy, Wolf Hall, said she had been caught by surprise when she was named the winner at a ceremony in central London.
She said: "Do you know I was completely astonished, not least by the chairman's brevity. I have heard chairmen who spend a lot more time in the limelight and go through each book and enumerate the merits of the judges and prolong the agony to the last minute so I was lolling in my chair and I feel a bit week at the knees to be honest."
Sir Peter Stothard, who chaired the judging panel, said the book which forms the second part of Mantel's trilogy on the life of Thomas Cromwell "utterly surpassed" the first volume.
He said: "She uses her art, her power of prose, to create moral ambiguity and the real uncertainty of political life, political life then and the pale imitation of political life now."
Mantel laughed off the praise, saying: "It is not the Olympics, it is not a competition, you are only as good as your last paragraph and I haven't written one of those today. This process can make you feel very much like an ex-writer or even when the praise becomes fulsome a dead writer."
Mantel, who has become a critical and commercial hit late on in her career, said she had "no expectations" of completing a historic hat-trick with the final volume of the trilogy which she is currently writing.
She said: "My publishers were always announcing my breakthrough book and it never really happened, it happened in terms of critical esteem, it didn't happen in terms of sales or impact on the general public, my fortunes began to turn when I met Thomas Cromwell."
Speaking earlier while accepting the prize, she said: "Well I don't know, you wait 20 years for a Booker Prize and two come along at once." She added she regarded the award as an "act of faith and a vote of confidence".
Bring Up The Bodies concentrates on the end of Henry VIII's marriage to Anne Boleyn and Sir Peter said it had made "one of the best-known pieces of English history" come alive again "as though for the first time".