Royal wills are never made public. That means what happens to much of the Queen's personal wealth following her death last week will remain a family secret. 

Forbes estimated last year that the late monarch's personal fortune was worth $500 million, made up of her jewels, art collection, investments and two residences, Balmoral Castle in Scotland and Sandringham House in Norfolk. The Queen inherited both properties from her father, King George VI. 

"[Royal wills] are hidden, so we have no idea actually what's in them and what that's worth, and that's never ever made public," Laura Clancy, a lecturer in media at Lancaster University and author of a book on royal finances, told CNN Business. But the vast bulk of the Royal family's wealth — totaling at least £18 billion ($21 billion) in land, property and investments — now passes along a well-trodden, centuries-old path to the new monarch, King Charles, and his heir.

The line of succession makes Prince William, now the first in line to the British throne, a much wealthier man.