Before Hellebæk, Utzon's built work amounted to a water tower in Svaneke on Bornholm. Everything else was drawings and prizes. His family had moved to Helsingør in 1937, when he was eighteen, and the stretch of coast between the town and the forest never really let him go. During the Second World War he went to Stockholm to study the work of Gunnar Asplund. In the winter of 1943–44 an exhibition of modern American architecture opened there, and Utzon found himself fixed on the houses of Frank Lloyd Wright. He went away and read Wright properly. What stayed with him was not a style but an argument: that nature and the particular character of a site should drive the building, that interior and exterior space are one problem rather than two, and that no project can be solved with a formula carried over from the last one. Every house, on that reading, has to be reasoned out from scratch.

He worked through several models, then built a full-size version in wood simply to stand inside it and judge how 130 square metres of living space would actually feel. The site made the decisions. Sun, view and shelter from the wind pointed the same direction, so the northern side became a completely closed wall and the southern façade became glass. That north wall went up first, to fix the geometry of everything that followed; kitchen and bathroom came next; the remaining rooms were divided by movable pinewood partitions and doors, so the plan could be rearranged later without touching the structure. Inside and out, the palette is identical — yellow-white brick, Oregon pine, aluminium. Hard-baked yellow tile runs along the tops of the walls and reappears in the kitchen, the grill niche, the shower and the fireplace. The children's rooms sit against the blind north wall and have no windows at all, a point critics have raised ever since. Utzon lit them from above, with skylights.

"It's my laboratory," he said of the house, and he meant it literally. Hellebæk stayed his base for the rest of his life. He was working from here when the Sydney Opera House competition came his way, and he won it in 1957 — an unknown Dane beating a field of established practices with a set of shells that nobody yet knew how to build. He resigned from the project in 1966, before it opened. The recognition arrived slowly and then completely: the Pritzker Prize in 2003, and by then a general agreement that the Opera House was one of the defining buildings of the century. Utzon died in Helsingør on 29 November 2008, at ninety, and was buried in the family plot at Hellebæk cemetery — a few minutes from the low brick house where the whole career started.

The imitation began almost immediately. Through the 1950s Danish architects borrowed the Hellebæk logic for one-family houses — the closed side, the open side, the modest single storey settled into its trees rather than placed on top of them. Halldor Gunnløgsson and Erik Christian Sørensen were among those working the same seam, and out of it came something recognisable as a national manner. Then the idea jumped scale. In 1958 Vilhelm Wohlert and Jørgen Bo finished the Louisiana Museum at Humlebæk, twenty kilometres down the same coast: a public building that wanders through a park in low glazed links, deferring to the landscape exactly as a private house had. Utzon put the principle plainly. "What is important for me," he said, "is that the architectonic approach or system behind a house should not limit the house's function and thereby hamper life inside." It is a strikingly humble sentence from the architect of Sydney Harbour — and it explains both buildings.