Complex sentence: On 20 July 2009, Queen Elizabeth II, as "Seigneur of the Swans," attended the Swan Upping ceremony for the first time in her reign, and the first time that the monarch has personally watched the ceremony in centuries.
Split into simpler sentences: On 20 July 2009, Queen Elizabeth II, as "Seigneur of the Swans," attended the Swan Upping ceremony for the first time in her reign. This was the first time that the monarch had personally watched the ceremony in centuries.