He admits that Poundbury is an expensive experiment, launched in the face of opposition from architects, planners, and economists. The high costs followed inevitably from his determination to avoid the mass-produced materials that give a dreary, uniform look. In Poundbury even the curbs are granite rather than the usual concrete blocks.

"It very nearly didn't end up like it is now because there were efforts to water it down," the prince said. "But we have probably shown that for a ten percent extra cost, roughly, you are actually achieving a far higher value in the longer term than the shorter term, which is the way the modern world looks at everything."

Indeed, Poundbury is so successful that it has spawned smaller versions of itself elsewhere in the duchy, and a bigger version is set to rise next to the Cornish town of Newquay. There the prince plans to incorporate, along with his "Poundbury principles" of design, advanced strategies for environmental sustainability, such as rainwater harvesting and geothermal technology. Experience gained at Poundbury should help. "It took a long time to wear down the public utility people to have one common trench for water, electricity, and gas," he said. "That was more difficult than you would believe possible. It means you don't have to dig up the road every five minutes—and, you know, one common satellite dish means you don't have to have these things stuck all over everything like a rash."

The prince's hope that his vision will shape urban living beyond the duchy seems to be coming true. The British government has embraced the Poundbury principles, and last year curious city planners and high officials from numerous countries, including the United States, walked Poundbury's streets. "Saudi Arabia is now going to come and have a look as a result of my encouraging," the prince said.

Prince Charles's duchy legacy stretches back a long way. On March 17, 1337, after "anxious meditation," King Edward III declared that his eldest son, the Black Prince, must henceforth enjoy an income worthy of an heir to the throne. So the king granted some of his castles, manors, and hamlets—largely in the counties of Devon and Cornwall—to his son, along with a spiffy new title: the Duke of Cornwall.

Most of the dukes left the tenants and lands alone. Not Prince Charles, who oversees the estate's work to an astonishing degree. His 72-strong duchy staff has learned not to build any new cottage, or fell an acre of woodland, without first seeking the royal nod. He sends Bertie Ross, his chief executive (officially, the Secretary and Keeper of the Records), a constant flow of detailed notes, handwritten in ink, with ideas or queries. But the day-to-day work of dealing with duchy projects and tenants is left to the staff, spread between the head office in London and four regional outposts managed by land stewards. They are long-serving men—all men—who have absorbed the thinking of "the boss" so deeply that most of them at times slip into his distinctive strangulated voice.