William (40) and Kate (40)

William and Kate, the Prince and Princess of Wales, are now the two most senior royals after the Charles and his queen consort Camilla (75).

William is first in line to the throne. “He really has to step up,” says Patrick Jepson, Princess Diana’s former private secretary. “In theory he could be king tomorrow. That’s the mindset that he and his advisers now have to be in.”

In 2021, William carried out 235 royal engagements, and that number could increase.

“We might see more joint working, and a degree of taking on duties to lighten the king and queen consort’s loads”, said Bob Morris of University College London’s Constitution Unit.

“There could be a higher degree of burden-sharing, particularly over foreign travel and the more arduous Commonwealth visits.

“The queen herself stopped travelling abroad in her eighties and, as Charles and Camilla age, it’s that kind of closer support we could expect to see.”

William is more comfortable with the idea of being the king-in-waiting, says Professor Pauline MacLaran, co-author of Royal Fever: The British Monarchy in Consumer Culture.

“I think we already see this in action, where he invited Harry and Meghan to join Kate and himself on the Windsor walkabout.

“He’s showing leadership and a sense of responsibility despite what his own internal emotions may be.

“I believe we’ll see him taking more responsibilities to assist his father in his new role of king.”