LONDON – Prince Charles turns 70 Wednesday and is still heir to the throne – a role he has served since he was a young child.

He is not lacking in things to do and shows few signs of slowing down – he is wealthy, extremely active in matters of great importance to him, and preparing to welcome his third grandchild into the world when Meghan, the Duchess of Sussex, gives birth next spring.

His destiny, however, is to be king, a position he will automatically assume with the death of his 92-year-old mother, Queen Elizabeth II.

When that happens, Charles will be bound by the constitutional requirement that the monarch refrain from trying to influence policy. Until then, Charles is free to lobby for action on climate change, support organic farming, and fight genetically modified crops as he sees fit.

The Prince's Trust, an ambitious charity, was founded 42 years ago.

Is the candle-crowded birthday cake a signal that it's time for the elegantly greying prince to take it easy? Not on your life, says Charles' wife, Camilla, the duchess of Cornwall.

"I do not think he thinks he's 70," she wrote in a tribute tribute to The Telegraph Magazine. "I think it's just a number to him." I keep saying you're going to be slow. . "

The royal family is in the midst of a slow, understated transition. The patriarch, 97-year-old Prince Philip, has formally retired from public life, although he makes occasional appearances in support of the queen.

For her part, the queen still maintains a busy schedule, but it does not make long haul flights to far flung parts of the 53-nation Commonwealth, and this year she took the unusual step of lobbying the Commonwealth countries to specify that Charles would be the next leader of the group, a position that is not hereditary.

The support for Charles has been unanimous, noting that Charles has a strong commitment to the Commonwealth.

Charles has also taken a more visible role in representing the Queen at some important national events, most recently during the Remembrance Day celebrations honoring Britain's fallen soldiers. He placed the queen's wreath at the foot of the Cenotaph monument while she watched from a balcony seat.

But his working trips and his speeches at home generate a little bit of energy.

In a way, Charles is sandwiched between generations, a symbol of dignity and continuity that has reigned since 1952, and his two immensely popular sounds, Prince William and Prince Harry, who have along with their wives come to symbolize the future of the world's best known monarchy.

William and Harry also reminded of their mother, the late Princess Diana, who died in Paris because of a crash in 1997 after a divorce from the British.

It is William and Harry – along with their wives Catherine, Duchess of Cambridge and Meghan – who appear on the cover of glossy magazines, not the about-to-be-70 Charles. It is the young royals who are seen as glamorous modernizers with the common touch, while Charles is sometimes perceived as dour, preachy and remote.

Camilla says the audience does not understand how "incredibly kind" and funny Charles is, and William and Harry – taking part in a rare BBC interview to mark his father's birthday – praise the way he has used his position Prince of Wales to advocate so many important causes, such as environmental protection.

But Harry – who has endeared himself to the British public in part with his impish smile and sunny outlook – urged his dad to cut back on the doom and gloom that often accompanies Charles' pronouncements.

"I would encourage him to remain optimistic because I think it can be very despondent and negative," said Harry. "But hopefully with his children and his grandchildren, and a few more grandchildren to come, he can get away from the family and then carry on his leadership role."

He also had this advice: do not work so hard, and have dinner earlier.