João - I use a library that provides access to the ILN archive and to many many other great resources, and suggest you join a major library with similar services.

Quite likely at the time of the visit to France, Queen Elizabeth the Queen Mother considered her crown as her own. It had been made specifically for her. But I do wonder if the Koh-i-nûr was actually on it to travel out of the UK.

Of course the Queen Mother also wore her crown without arches to the coronation of her daughter.