Thirteen books, thirteen storeys of story apiece: when Terry Denton and his writing partner, Andy Griffiths, added up the arithmetic on their Treehouse series, it came to a tidy 169, and the two men agreed that was exactly the right place to stop. Denton, the Australian illustrator who drew every one of those storeys, died near Melbourne on September 21, 2026, surrounded by his family. He was 76. By then the series he built with Griffiths had sold more than 10 million copies worldwide and reached readers in more than 35 countries, according to ABC News and Pan Macmillan.

Denton and Griffiths were already old collaborators by the time they climbed into that treehouse. They met in the early 1990s, when Denton, then working as a freelance illustrator, took on a pair of educational short-story collections meant to liven up classroom writing lessons, Swinging on the Clothesline and Rubbish Bins in Space. Griffiths later described what Denton brought to the partnership, recalling that Denton "had a window into my brain and he could find that weird nexus between the everyday and the fantastic," and that the work "allowed him to unleash his inner anarchist," as reported by the Illawarra Mercury. "It's really been a dream come true," Griffiths said of their partnership. In 1997 Denton illustrated Griffiths' first trade book, Just Tricking!, and the two writers, one with words and one with a pen, kept working together for the rest of Denton's life, later publishing Once Upon a Slime, a writing-and-drawing activity book that gave readers a behind-the-scenes look at their creative partnership.

The treehouse itself did not arrive until 2011, with The 13-Storey Treehouse. Griffiths added thirteen storeys with each new book, and Denton drew all of them: the catapults, the underground laboratories, the ever-expanding cast of characters squeezed into gatefold spreads. The 78-Storey Treehouse, published in 2016, became the fastest-selling book in Australian publishing history on its first day of sale. Stage versions of the books sold out runs at the Sydney Opera House, and the series was eventually published in more than 35 countries. The series finally reached its thirteenth and last book in 2024, The 169-Storey Treehouse, closing out a run of 169 stories, 13 books of 13 stories each, a number Griffiths said the pair had long joked about and, to their own surprise, actually hit.

Denton had spent decades finding his way to that drawing table before Griffiths ever showed up. Born in Melbourne in 1950, the second youngest of five brothers, he later described the household that shaped his sense of humour: "Trained from childhood in a home of five boys and a mad mother; humour was our ritual." He studied architecture at university, grew disillusioned, and left, spending the next several years moving between painting, sculpture, cartooning, etching, theatre and animation, working part time in a music shop along the way, according to his own biography. His first solo picture book, Felix and Alexander, was published in 1985 and won the Children's Book Council of Australia's Picture Book of the Year the following year, establishing him as an author-illustrator well before he ever met Griffiths. Over his career Denton wrote, illustrated, or both for more than 40 books of his own, including the Gasp! series later adapted for television, illustrated for other prominent Australian writers, among them Mem Fox, Paul Jennings and Gillian Rubinstein, and collected more than twenty children's choice awards along the way.

In recent years Denton lived by the beach in Mornington with his wife and several dogs, and liked to joke, according to his own biography, that his primary hobby was simply working in a darkened room, drawing. His death was announced by his literary agency, Curtis Brown, and his publisher, Pan Macmillan, who said Denton died near Melbourne, surrounded by his family. He is survived by his wife, Kristen, their children Imogen, Eve and Max, and five grandchildren, Georgia, Lucy, Charlie, Alfie and Felix.

Griffiths, his collaborator of more than three decades, kept his own tribute short: "I'll miss him forever, but he's at peace now." He also called Denton a natural clown, adored equally in life and in the pages of the books the two men made together, and said working and playing alongside him for thirty years had been an honour. In a statement, Denton's children said his work had given joy to millions of children around the world, adding: "We are so grateful that his stories will continue to live on, bringing wonder, laughter and comfort to generations yet to come."

What Denton leaves on the page is countable: 13 Treehouse books published in more than 35 countries and staged as sellout productions at the Sydney Opera House, more than 40 books of his own devising, and decades of drawings made for other writers' words. His pictures gave the Treehouse world its shape, down to the smallest joke hidden in a margin, and that world, still selling and still read aloud at bedtime, carries on without him.