The photo was taken during a shoot that lasted just a few minutes and is understood to be one of the last frames after the King finished posing and went straight back to work.
He sits at a 19th-century French mahogany writing desk, in front of a painting of James and Leo with Their Sons, Francesco Zuccarelli 1743, acquired by George III for the royal collection.
The red box is placed on a gilded wood stool made by Henry Williams in the mid-18th century.
In the background is a typical black and white photo the late queen and the Duke of Edinburgh, which the young couple gave to King George VI for Christmas in 1951.
New custom red boxes are currently being made the kingwith six boxes that will carry his royal cipher.
They will contain documents from UK and Kingdom government ministers and Commonwealth representatives sent from his private secretary’s office to the king, wherever he is in the world, in a locked red box.
Further papers, one tied with tape, are visible next to him.