The new Prince of Wales, followed by the Queen Consort, entered the Picture Gallery and stepped into the forefront. William, 40, was seen putting out a guiding hand behind his stepmother Camilla, who now bears the style Her Majesty, as she almost missed her step.
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The pair signed the declaration for King Charles in the opulent room which was packed with some 200 Privy Counsellors.
Prince William – now heir to the throne – cast his eyes down as Lord President of the Privy Council Penny Mordaunt opened the proceedings, discharging her "sad duty" to inform those gathered of the passing of Her "Most Gracious Majesty Queen Elizabeth II".
Camilla, dressed in black and wearing a three-strand pearl necklace, stared straight ahead, surveying the scene, as six former prime ministers, the entire Cabinet, and religious and political leaders past and present listened intently to the ceremony.
The moment Prince William reached out to help the Queen Consort
There was utter quiet as the words echoed around the grand room, with its deep scarlet flocked walls and imposing oversized portraits of previous monarchs including King William III.
Yet the grandeur and importance of the first part of the Accession Council was in stark contrast to the scene just moments before when the room had buzzed with noise and the loud chatter of conversations.
William was the first to sign the Proclamation, carefully stepping forward to pick up the pen with his left hand before placing his signature on the historic record, as he replaced the lid and set down the pen. He was followed by Camilla, who slowly signed her named with care.
Her eyes darted briefly towards William as she returned to his side on the dais. The Prince moved back and forward just a touch as he stood there with his hands clasped, with the grieving pair both solemn but in control of their emotions.
As the order of business for the proclamation was set out, William gazed upwards at the ceiling surveying the grand surroundings – in the palace he knew well as a child. With the short proceedings at a close, William acknowledged Prime Minister Liz Truss as the party made their way through to the Council Chamber for the second part of the Accession Council.
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