I really like Queen Camilla's crown (it reminds me of Empress Zita's). But (personal opinion here) I don't think it looks quite right next to the King wearing the Imperial State Crown. The banner picture on this board is a constant reminder to me of this mismatch. The problem lies in the fact Queen Elizabeth II had the Imp State Crown shortened in order to "look more feminine". Which was absolutely fine for QEII, because her consort, Philip, didn't even get to wear a crown, and thus there was no "competition" as it were (of his crown being taller than hers). Charles has presumably decided not to have the Imp State Crown restored to the taller shape enjoyed by George VI (google images from his coronation, on the balcony at Buckingham Palace, to see how much taller the original crown was). Which leaves a situation where, to my eye, Camilla's crown looks somehow "grander". If Camilla wears the Diadem for the whole State Opening of Parliament, the problem is sidestepped; but if she wears her own crown, I feel the "mismatch" will look jarring. (All my own personal opinion. For what it's worth.)
We won't know either a few days before the occasion or on the actual day. Personally I think the King will wear the Imperial State Crown. The Queen may wear hers as well, but I think the State Diadem will make an appearance.
King George VI and Queen Elizabeth did wear their crowns at the State Opening of Parliament in 1937. Also full robes. Information can be found in this PDF link to the Winnipeg Evening Tribune, 26 Oct 1937.
https://digitalcollections.lib.umanitoba.ca/islandora/object/uofm%3A1827600
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