There will be an “inevitable” reduction in royal engagements after the Princess of Wales joined the King in sharing her cancer diagnosis, an expert on the monarchy has said.

The managing editor of Majesty magazine Joe Little said it was a “significant moment for the monarchy” that two senior figures should be out of action, adding that Kate’s announcement on Friday evening was a “great shock” to many people.

He said the Queen’s profile had “come to the fore” in recent weeks because she has had to attend more engagements alone.

Mr Little told the PA news agency: “The statement was a great shock to so many people because the feeling was that the Princess of Wales was over the worst and on the road to recovery.

“I don’t think anybody expected her to tell us in such a direct personal way that she has cancer.

“It’s a remarkable situation and a significant moment for the monarchy and the institution so early in the King’s reign that two senior figures should be out of action.”

Mr Little said it was “inevitable” that the number of royal engagements would have to be reduced, adding “the royal diaries will have been revised anyway because of these health considerations”.

He said public engagements were “clearly not on the cards for some time” for both Charles and Kate, adding that the Princess’s situation was “complicated” by her young family.

Mr Little noted that the “time of British pomp and pageantry” in June was approaching with “all manner of high profile events” such as the King’s birthday parade, also known as Trooping the Colour, and Royal Ascot.

He said he “did not anticipate” the Queen’s diary getting any busier than already planned, but added Camilla would “certainly” be attending engagements “she otherwise would have not done on a solo basis”.

This includes the annual Maundy Service on March 28 where Camilla will be distributing the Royal Maundy gifts on behalf of Charles at Worcester Cathedral.

The managing editor of Majesty magazine since 1999 added: “The number of engagements that she is undertaking hasn’t increased, but her visibility and her profile has come to the fore because she is currently the most senior member of the royal family operating.”

Mr Little said support would “always be there for the Queen” from other members of the royal family, just “not the physical presence” on such engagements.

He added that Charles’s slimmed-down monarchy approach meant “the pressure is on a much smaller team”.