What historical event begins the first episode of Downton Abbey?

The historical event that begins the first episode of Downton Abbey is the sinking of the Titanic.

The episode opens in April 1912, immediately after news arrives that the RMS Titanic has sunk on its maiden voyage. The disaster killed more than 1,500 people, including Patrick Crawley and his father, James Crawley, who had been expected to inherit the Downton estate.

Their deaths create the central inheritance crisis of the opening story. Because the Crawleys have three daughters but no son, the estate is tied to a male-line entail. The next heir is therefore Matthew Crawley, a distant cousin and solicitor from Manchester whom the family has never met.

A common mix-up is to confuse the Titanic with the later First World War, which becomes the major historical backdrop near the end of the first series and dominates the second. The Lusitania was sunk in 1915, three years after the event that launches the drama.