RMS Lusitania
From Tardis Wiki, the free Doctor Who reference
The RMS Lusitania was an ocean liner that was torpedoed by a German U-boat on 7th May 1915, an act that helped provoke the United States into entering World War I two years later. The Doctor failed to prevent the ship from being sunk. (BFA: The Sirens of Time)
In an alternate timeline, the Lusitania was not sunk due to the Doctor's intervention. (BFA: The Sirens of Time)
