King Charles has suffered a blow as Prince Harry has failed to avoid a clash with the monarch’s upcoming royal tour. The Duke of Sussex, 39, is finally set to bring out the paperback edition of his memoir, Spare. However, its October release will clash with King Charles’s high-profile appearance at the Commonwealth Heads of Government Meeting in Samoa. This is the first time he will be attending since acceding to the throne and becoming head of the global organisation. The meeting will be held between October 21 and October 25, with Harry’s paperback being published in the US on October 22 and…