Earl Spencer says that he can see echoes of Princess Diana's treatment from the press in the way Harry and Meghan are scrutinised.
A TV news presenter has been named as the traditional kingdom of Tooro's new monarch but the late king's family claim he chose an heir.
Auction house Sotheby's expects the dress to sell for up to $300,000 (£220,000) when it goes under the hammer on 9 December.
Tens of thousands of people lined the streets to pay their respects after 13 days of national mourning.
President Donald Trump said he was not a fan of the couple and added that they treated the Royal Family with "great disrespect".
Norway's new King takes the first major step of his reign as his father, the late King Harald V, lies in state at the Royal Palace.
From Suffolk to Saudi Arabia, Julius Smith recalls serving in some of the world's wealthiest homes.
Mourners gather outside the palace as royals, politicians and citizens remember a beloved king, whose son has adopted the family motto "all for norway".
King Oyo ascended to the throne of Uganda's Tooro kingdom when he was just three years old.
