Your Grace

title used when addressing a nobleman or person of high rank (such as a duke, duchess or archbishop)

His Grace or Her Grace was the style used to address the monarch of Scotland up to the Act of Union of 1707, which merged the Kingdom of England and the Kingdom of Scotland, and to address monarchs of England prior to Henry VIII. Today, the style is used when referring to non-royal dukes and duchesses in the United Kingdom.
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