Charles, then still Prince of Wales, opened Parliament on his mother’s behalf this May. He was not allowed to wear the Imperial State Crown for this occasion; it was carried in on a pillow and placed next to him on the throne, but he didn’t get to wear it, which makes sense since he was only deputising.
But suppose Charles opens Parliament next year before the coronation takes place. Would he get to wear it? It’s “his” crown now (not in the sense of ownership, but in the sense that he holds the office whose power the crown symbolises), and he’s full-fledged King now since the moment his mother died; on the other hand, the crown has not been ritually placed on his head yet.
Good question, and thank God for Google. We have two recent precedences - Edward VIII, who only attended one State opening and never got crowned, and The Queen herself, who attended in 1952.
Neither wore the Imperial Crown, and the Queen, instead, wore the George IV State Diadem (source, with pictures). That’s the one that appears on our stamps.
So the lack of a ceremonial coronation with divine blessing beats the status as a legitimate hereditary monarch as far as wearing the crown is concerned. Ignorance fought. Thanks!
Another difference is that if it happens before the Coronation, the King will have to swear an oath declaring that he’s a protestant and will uphold the protestant succession to the throne before he gets around to reading the speech. (Up through the reign of Edward VII, it was a tediously long and sectarian oath that went into great detail about what Catholic doctrine got wrong. George V demanded that it be shortened.)
It is not completely unknown for a monarch to wear their crown when opening Parliament before their coronation - Charles I did so - but the tradition is that they don’t.
