Allow me to dip into my list of Tiaras I'd Like to See Resurrected for a moment, will you? Languishing in the vaults somewhere, the British royal family has this gem:
Mary left the tiara to Queen Elizabeth (later the Queen Mother). She never wore it in public, but she did loan it to her daughter Princess Margaret.
I think this one's a natural suggestion for Kate. (Not for the wedding, but perhaps later.) She already has the sapphire engagement ring. Plus, it would go great with some of the Windsor's sapphire pieces that I don't think we see enough of.