The late Princess Diana on the Maid of Mist in Niagara Falls in 1991 with her sons Prince Harry, then 7, and Prince William, then 9. A slew of lost letters from Princess Diana to a palace confidante provides an intimate look at the childhoods of William and Harry. Already at age eight, it emerges that Prince Harry was developing the cheeky rebellious streak he’s become known — and loved — for.