LONDON (AP) — A crowd cheered, hundreds of cameras clicked and an image of familial perfection was beamed around the world.Prince William, his wife Kate and their infant son, the Prince of Cambridge, emerged Tuesday from London's St. Mary's Hospital to start a new chapter in their lives — capping a remarkable turnaround for a monarchy that had ended the 20th century at a low point of popularity.The outpouring of public and official enthusiasm — including artillery salutes, marching bands and landmarks illuminated blue for the royal baby boy — showed that Britain's royal family is back in its subjects' affections, especially now that it has an adorable infant heir, third in line to the throne, who could be king into the 22nd century.Pictures of William, Kate and their baby, whose given names have yet to be announced, echoed a similar image taken 31 years ago, when Prince Charles and Princess Diana left the same hospital with baby William in their arms.William and Kate looked much more relaxed than the awkward Charles and Diana, and within a few years the older couple's image of regal domestic bliss had been comprehensively trashed.The baby adds a new layer of stability to help the institution thrive for another generation. For the first time since the 19th-century reign of Queen Victoria, Britain has three generations of living heirs to the throne — Prince Charles, William and his baby son.Through Kate, the future king also has a dose of non-royal blood. Her family, although affluent, comes from an ordinary, middle-class background."I think this baby is hugely significant for the future of the monarchy," said Kate's biographer, Claudia Joseph.