On 28 Mar 2003, Cathy Madewell from Cincinnati, OH wrote

Dear Departed Di,
How do you correctly address a former President of the United States?

The accepted form of address for a former President of the United States of America is “Former George W. Bush,” for example.

May I take this opportunity to say how nice it is to see young people showing an interest in the correct forms of address.

Yours sincerely, Diana

Former Princess of Wales