"Peter I or Peter Frederick Louis of Holstein-Gottorp (German: Peter Friedrich Ludwig von Holstein-Gottorp) (17 January 1755 – 21 May 1829) was the Regent of the Duchy of Oldenburg for his incapacitated cousin William I from 1785 to 1823, and then served himself as Duke from 1823-1829.
He also served from 1785 to 1803 as the last Lutheran Prince-Bishop of Lübeck, until that Prince-Bishopric was secularized and joined to Oldenburg. His son, Augustus, was the first Duke of Oldenburg to use the style of Grand Duke that was granted in 1815." - (en.wikipedia.org 30.01.2020)
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