Tale of Henry's favourite is a winner with the bookies – and the Booker

Bookmakers had predicted her victory as a near certainty, but some were less convinced. As previous contestants have all too painfully learned, being a frontrunner for the Man Booker Prize can amount to little more than a kiss of death ahead of judgement night.

But last night, Hilary Mantel proved the doubters wrong. Wolf Hall, her epic historical tome about Thomas Cromwell, adviser to Henry VIII, had been the clear frontrunner for weeks and was a deserving winner of the £50,000 prize.

Mantel, 57, from Derbyshire, who has served as a Booker judge herself, said she had feared that her book's popularity could work against her in the end. "Having been a judge in 1990, I know anything can happen in that final meeting. I know being the favourite can weigh on the judges, and it can work in the opposite way," she said.

Mantel revealed she first had first had the idea of the book some 30 years ago. "I hesitated for such a long time before beginning to write the book ... actually for some 30 years. I could not have written the book back then, a book about a seasoned hardened political campaigner in his 50s," she said.

She explained that her book was a study of power, told through the biography of Thomas Cromwell, the son of a blacksmith who rises to wield immense power in King Henry's court and finally becomes the architect of the Reformation "The exercise of power, the business of obtaining power, how it is won and lost ... we are still living in a Machievellian world," she said.

Pondering her words, James Naughtie, chair of the judges for the prize, asked Mantel: "Have you sent the book to Peter Mandelson?"

Weighing in at more than 650 pages, the book has already proved so popular with the public that it threatened Dan Brown's pole position on one bestseller list. The judges praised it as a commercial success that could also garner critical recognition on a powerhouse shortlist that included a former Booker winner, AS Byatt, and the twice Booker and Nobel Prize recipient, JM Coetzee. Not since Yann Martel's Life of Pi won the prize in 2002 had a frontrunner claimed such a bold victory.

Naughtie praised Mantel's work for being surprisingly contemporary despite its historical roots in the Tudor revolution of the 1530s. "Our decision was based on the sheer bigness of the book; the boldness of its narrative; its scene-setting; the extraordinary way Hilary Mantel created a contemporary novel that happens to be in the 16th century," he said. But he made clear that Mantel had faced formidable contenders during the three-hour decision-making process. "It was like looking at an Alpine landscape and looking for a peak that was just a little bit higher. That does not mean that the other vistas will not be remembered in another 100 years," he said.

He also noted that many of this year's choices had proved to be runaway commercial successes, which he put down to the "Me Cheeta effect" –referring to the celebrated spoof autobiography of a chimpanzee turned Hollywood celebrity which also made the longlist.

Global voices: The past four winners

2008 Indian journalist Aravind Adiga's debut novel, The White Tiger, charts India's rise as a global economic force. The lead character, Balram, comes from crushing poverty but refuses to be defined by the country's caste system.

2007 Irish writer Anne Enright, widely considered an outsider, scooped the prize for The Gathering. The novel depicts an Irish family gathering for a wake, where a relative of the deceased uncovers their troubled past.

2006 Indian author Kiran Desai won with The Inheritance of Loss. Set in the 1980s, the novel explores issues of migration and globalisation. It takes place in a Himalayan town near Mount Kanchenjunga and New York.

2005 Winner was Irish novelist John Banville's The Sea, narrated by a retired art historian who confronts his past in a town where he spent a childhood holiday.