Historically, monarchs weren't supposed to be great orators, were they? They had to craft their messages with some care, but good delivery was not really a part of the package. More important was to use words that sounded regal.
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After the coming of TV and radio, presentation became a tad more important, but some of the royals resisted the notion of being in league with actors or pitchmen or base politicians. That said, there are some who have worked on their skills, and some who have not worked quite so hard.
Queen Elizabeth is not a great orator, but neither is she awful. She is, however, somewhat old-fashioned. In particular, she remains largely dependent upon a script and does not try to make it look as if she speaks unscripted.
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