Eleanor Catton was last night awarded the 2013 Man Booker Prize for her novel The Luminaries (Granta in the U.K.; Little, Brown in the U.S.), described by Robert Macfarlane, chairman of the jury, as "a magnificent novel: awesome in its structural complexity; addictive in its story-telling and magical in its conjuring of a world of greed and gold."

The Canadian-born author is only the second New Zealander to win the award (the first was Keri Hulme with The Bone People in 1985, a controversial choice and one of the poorest-selling winners) and she enters the record books as the youngest ever winner, beating Ben Okri, who was 32 when he won in 1991 with The Famished Road. And in contrast to that notorious 1991 all-male shortlist which led to the founding of the Orange Prize for Women's Fiction, four of this year's contenders were women. Another record.

At the press conference which followed the dinner presentation, Catton expressed support for the broadening of the Prize's remit, but there is concern that, however garlanded, it will be harder for "quieter" Commonwealth writers such as herself, or Kiran Desai, to win against the onslaught of more "muscular" American fiction. This is the last Man Booker Prize to be presented under the old rules and Catton's winning of it seemed somehow appropriate. Now worth £50,000, the award which began life as the Booker Prize, its remit shaped by Booker McConnell's trading interests, is in its 45th edition.

The Luminaries, set in the 1866 New Zealand gold rush, is a door-stopping 832 pages, surely the longest winner. It was apparently a unanimous choice - or at least no vote was required. Macfarlane appears to have been an exemplary chair. From first to last, the best kind of intellectual argument was punctuated with good humour. At the final meeting, jurors - biographer and critic Robert Douglas-Fairhurst, writer, broadcaster and comedian Natalie Haynes, political journalist and broadcaster Martha Kearney and critic and reviewer Stuart Kelley - were required to discuss each of the novels without any indication as to their preferences. By the end of two hours, The Luminaries had emerged as the clear winner.

Praising the faultless "integrity, diligence and acuity" of the jurors, Macfarlane reported that they had read 151 novels, passing through landscapes of "great strangeness". He and his colleagues felt by turns "appalled, amazed, saddened, bored, confided in and betrayed". Macfarlane the walker estimated that they had read some 20 kilometers of prose "as measured in 12-point Garamond. It was an exhausting and fascinating journey." The very best reminded them of the power of the novel "to secure passage into regions of the kind otherwise inaccessible." He quoted Milan Kundera on the novel, "that knowledge is its only morality as a form". Their shortlist comprised "six extraordinary novels" and finding a winner hadn't been easy, he concluded before announcing the decision.

One gracious speech led to another, Catton - taking a moment to collect herself at the table before stepping up for the presentation by the Duchess of Cornwall - started nervously, an audible tremble in her voice as she thanked everyone who had made her success possible: family and friends as well as her original Kiwi publisher Fergus Barrowman of Victoria University Press; her agent Caroline Dawnay of United Agents; Sara Holloway, who had signed her to Granta with a two-book contract; Max Porter to whom she had been handed over; Philip Gwyn Jones, one of the many who has lately parted company with Granta; and owner Sigrid Rausing, seated somewhere in the Guildhall.

As she spoke from her prepared text, she grew in confidence, joking that she was "a publisher's nightmare". She was, she said, "aware of the pressure on publishers to make money" but hers had left her feeling "free to concern myself with the question of value, not of worth". Catton said she had been sustained by the "intellectual consistency and rigor" of those she'd worked with.

As she stepped down from the podium, Colm Tóibín, shortlisted for the third time with The Testament of Mary, was among the first to congratulate Catton, embracing her warmly. He was followed by Ruth Ozeki, something of an outsider with A Tale for the Time Being.

Introducing the proceedings, Jonathan Taylor, Chairman of Booker plc, described the shortlist as "a celebration of the glory of the English language in all its vigor, its vitality and its versatility. The home and hinterland of literary fiction in English must be the English language and it should not be constrained by passports and border controls."

Granta's Ian Chapple, sales and marketing director, reported that the novel had sold 60,000 copies, U.K. and export, before the prize; a 50,000 reprint, "for starters" was ordered in the wake of the announcement. LB just released the book in the U.S. October 15.