Napoleon accepted the crown of the newly created kingdom of Italy in a grand ceremony in the throne room at the Tuileries on Sunday, March 17, 1805, Andrew Roberts explains (in Napoleon: A Life), and then proceeded to Milan, for another coronation ceremony at the Duomo:
‘The church was very beautiful,’ Napoleon reported to Cambacérès. ‘The ceremony was as good as the one in Paris, with the difference that the weather was superb. When taking the Iron Crown and putting it on my head, I added these words: “God gives it to me; woe betide any who touches it.” I hope that will be a prophecy.’ The Iron Crown of Lombardy, a heavy oval band of gold containing metal supposedly from one of the nails of the True Cross, had been worn by every Holy Roman Emperor since Frederick Barbarossa in 1155. Napoleon’s use of it was thus a further sabre-rattle against the present incumbent, Francis of Austria.