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.
Britons are being urged to turn their lights off for an hour tonight to mark the centenary of the First World War.
The 14-18 NOW Lights Out campaign hopes people will leave a single light on between 10 and 11pm to mark the exact hour when Britain declared war on Germany.
But don't worry - the campaign's website says that light can be your TV, laptop or mobile phone.
Are you joining in the "moment of reflection"? Post your pictures on our Facebook page.
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.