Talk about an apprentice. By the time he turns 60 Friday, Prince Charles will have spent a lifetime in line to become king.

That's put him in quite a bind. The longest-waiting heir in British history only ascends to the throne when his beloved mother dies or decides to step down.

Queen Elizabeth II hosted a birthday party for her son Thursday at Buckingham Palace. The Philharmonia Orchestra, of which the prince is patron, played for invited members of his extended family, European royalty and assorted society figures. Charles' wife Camilla was throwing a more private bash on Saturday at the prince's rural estate, complete with a performance by sexagenarian rocker Rod Stewart.

But the queen won't be giving Charles the present many believe he craves most — the crown. The queen has indicated informally that she plans to keep the job for life and some people think the 82-year-old monarch intends to live forever, or at least as long as her mother, who died at 101.

"It can't be easy," said historian Andrew Roberts. "Most of us can look forward to our new jobs, but the circumstances under which her reign comes to an end means that he can't, emotionally and psychologically."

If the queen remains in good health, Charles may be nearing 80 — or past it — when he fulfills the unique destiny that was his at birth.

Britain's next-longest monarch-in-waiting was Queen Victoria's eldest son, who became King Edward VII in 1901, aged just over 59 years and two months.

But shed no tears for old Charles and his predicament. He has made being Prince of Wales a pretty good thing.

Experts, associates and friends say he realized decades ago that he would make his mark as Prince of Wales rather than as an octogenarian king, and so decided to expand that undefined role and use it to pursue causes dear to his heart.

Roberts said Charles has transformed the traditionally weak role of Prince of Wales — which the historian compared to the vice-presidency of the United States — by using it as a bully pulpit.

"He's made a real job of it," Roberts said. "He's spoken out on what matters most to him, championing organic food over genetically modified crops, backing architecture that is human in scale, pursuing better relations between the Islamic world and other faiths, and starting the Prince's Trust, which has helped many young people in trouble."

The princely role offers a few advantages over being monarch. Some say the money is better, because the Prince of Wales controls the lucrative Duchy of Cornwall, the 55,000-hectare (136,000-acre) estate established in 1337 by King Edward II to provide income for his heir. Official accounts show the prince's property and investments brought in 16 million pounds (US$24 million) last year.

And a prince is much more able to speak his mind than a king or queen because of constitutional restraints placed on the person heading the House of Windsor.

Patrick Jephson, former private secretary to Princess Diana, said Charles' income from the Duchy of Cornwall allows him to spend a "colossal" amount of money building his empire and pursuing his interests and causes.

"In effect, he is king now in his own kingdom," said Jephson. "He has all the trappings and enjoys all the perks and one might argue none of the responsibility. This takes some of the sting out of having to wait. You can say it's awful because your promotion depends on your mother's death, but we've all had parents die and not benefited so spectacularly from it."

Jephson finds Charles arrogant in many ways. But he has some sympathy for the aging prince.

"He is trapped between an immovable object, his mother, and the ever rising profile of his photogenic and sexy children," Jephson said. "That's all the more reason to feather your nest while you can and enjoy being master of all you survey."

There is no doubt that Charles is less popular than the queen, who commands wide respect throughout Britain for her unswerving devotion to duty for more than half a century. She became queen on the death of her father George VI in 1952. Charles, the eldest of her four children, was not yet 4 years old.

Charles' many detractors see him as a slightly potty eccentric who talks to his plants and is so committed to environmental causes that he converted his vintage Aston Martin to run on surplus wine.

Some still fault him for the spectacular flameout of his marriage to Princess Diana and his not-too-carefully-concealed extramarital affair with Camilla Parker Bowles, now his second wife.

His image has been hurt by unauthorized leaks about his gilded lifestyle, including reports that one of his aides squeezes his toothpaste onto his toothbrush for him.

This negative view has led a boomlet of support for the idea that Charles should forgo the chance to become king at an elderly age and instead pass the crown to Prince William, his dashing eldest son.

But that idea will never fly, said Vernon Bogdanor, a professor of government at Oxford University who has written extensively about constitutional matters.

"That's not possible without legislation in Britain and 15 other Commonwealth monarchies," he said. "The monarchy is not seen as something you can choose to accept or not."

Bogdanor concedes that Charles' reputation was at a low point after his disastrous divorce from Diana, and polls show he remains less popular than the queen. The Daily Mirror newspaper summed up many Britons' feelings Thursday in an editorial. "Happy birthday, Charles," it said, "but long may the queen reign over us."

But Bogdanor said the public view of the prince has improved since then. Charles has lectured around the world on the environment, championed interfaith dialogue and channeled millions to good causes through his Prince's Trust charity, which helps young people get education, work and training.

"He's the first heir to the throne to find a role for himself," Bogdanor said.

"He's connected with outsiders the politicians sometimes ignore. I think now people appreciate what he's done. He could have sat back and done nothing."