The Prince of Wales made history when he opened the new session of Parliament alongside the Duke of Cambridge and gave a glimpse of his future role as head of state.
Joe Little, managing editor of Majesty magazine, said standing in for the Queen was a "duty" Prince Charles "would rather not have had to fulfil but nevertheless that’s what he and William were there for as Counsellors of State".
In the absence of the Queen, the heir to the throne and his son provided a sense of continuity amid the pomp and ceremony, and Charles’ reading of the Queen’s Speech was a highly symbolic occasion.
With Her Majesty's advancing years, the move has been interpreted as a significant shift in the prince’s responsibilities in his role supporting his 96-year-old mother.
The monarch reluctantly pulled out on the advice of royal doctors due to her continued mobility problems and delegated her role to Charles and William, but watched the proceedings on television from Windsor Castle.
The Prince of Wales and the Duchess of Cornwall at the Palace of Westminster. Aaron Chown
The Prince of Wales sits by the Imperial State Crown. Ben Stansall
The royal expert described the occasion as a “big moment in royal history”.
Mr Little said of Charles: “It must have been a hugely significant moment for him.
“It was rather telling the way that as the Imperial State Crown was placed on the table at the side of him, he looked at it for several seconds.
“You kind of wondered at the time what was going through his mind.
“As people have been saying today, we’re looking at the future.
“It’s a big moment in royal history.”
At the State Opening the 73-year-old prince sat not on the sovereign’s throne, which had been removed, but on the consort’s throne, which used to be occupied by his father, the Duke of Edinburgh, and which Charles has used in recent years.
A space remained next to him, where the Queen’s missing throne is usually located, under the opulent canopy, with the monarch’s Imperial State Crown in front on a velvet cushion.
On either side of Charles were William, in a morning coat, and Camilla, wearing a day dress and hat, in the Chairs of State.
The ceremony was a first for second-in-line to the throne William, 39, who will also one day be king.