This was my question, and I confidently gave the answer that, fortunately for me, was on the question sheet – and I was awarded the points. And yet it appears that both the question setter and I were at best only partly right.
The line "the shot heard round the world" was actually written by the American poet Ralph Waldo Emerson, in a poem that was written in 1837 for the dedication of a monument commemorating the Battle of Concord, which was the second in a series of battles and skirmishes on 19 April 1775, at the outbreak of the American War of Independence.
Wikipedia adds that in Europe and the Commonwealth, the phrase is most associated with the assassination of Archduke Franz Ferdinand.
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