Britain's most famous landmarks including the London Eye, Houses of Parliament, Downing Street and Gateshead's Millennium Bridge were plunged into darkness for an hour last night to mark the moment Britain first declared war on Germany in 1914.
Royalty, political leaders and relatives of fallen soldiers united tonight to remember the sacrifices and losses 100 years on from Britain's entry into the First World War.
A moving twilight ceremony at St Symphorien military cemetery near Mons, Belgium, was the highlight of a day of events.
ITV News Europe Editor James Mates reports from Mons:
As the Lights Out event to remember those who fought and died in WWI happened last night ITV asked our viewers what they did to take part.
Lights on some of Britain's most famous landmarks were extinguished between 10pm and 11pm to remember those who died in WWI.