Her Majesty Queen Camilla takes the lead in this Monarchy, wearing Her Majesty the Queen's George IV Diadem. Compared to some of Her Majesty's tiaras, this looks small.
Here is the link to the BBC coverage of the royals in pictures.
YouTube has the full speech.
The State Opening of the British Parliament is one of the few times the king wears the crown. In most other monarchies, including all the European ones, the crown rests on a table and is not worn, because those monarchs are now crowned or announted but only sworn in.