World War One: Lights turned off to mark 100th anniversary
4 August 2014 Last updated at 22:58 BST
Lights have been turned off around the UK in memory of the 17 million soldiers and civilians who were killed between 1914 and 1918 in World War One.
Royals and world leaders gathered on Monday for ceremonies marking 100 years since Britain joined the war.
Huw Edwards reports.