'Swan Song': New book by Princess Diana's brother drops

Charles Spencer's book about his late sister Princess Diana's life and former marriage to Britain's now King Charles III hit bookstores on Tuesday.

The book titled  "Swan Song: Diana, My Sister" is being published globally by Penguin and has been translated into 12 languages.

The memoir triggered a royal row even before it went on sale, after some of its pre-published extracts —  laden with Spencer's explosive claims  —  received a rare reaction and rebuttal from the king.

Charles Spencer, the 9th Earl Spencer, is Diana's younger brother and has long clashed with the royal House of Windsor over how they treated the princess.

In one of the claims that made a splash ahead the new book's release, Spencer accused Charles of sounding "giddily elated" and "like a lottery winner" when he had called him after Diana's death.

Spencer also writes that he had argued against plans for Charles and Diana's sons, William and Harry , to walk in their mother's funeral procession in 1997, saying that she would not have wanted them to go through that ordeal.

Spencer claims Charles "went ballistic" during the argument , telling him: "Rest assured, we'll forget her soon enough."

The world was moved by somber visuals of the young princes walking behind Diana's coffin.