Despite the mountains of documents released since its publication, and a mountain of criticism of his conclusions, Posner says there is no plan to update it, other than perhaps including a new foreword.

NPR: 50 Years On, Finding Profit In 'Truth' On JFK Case

Welsh-born Prime Minister Julia Gillard, a republican, has for her part conceded that the issue is unlikely to be tested again during the lifetime of the current British monarch, a view shared by Mr. Turnbull, who along with Mr. Swan wrote a foreword for the new book.

WSJ: Australia Lawmakers Seek Split From U.K. Monarchy

He has written a foreword to the charity's new book launched on Thursday night, at Camden Arts Centre, London.

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