David Cameron said the First World War "profoundly changed our world" as he paid tribute to the sacrifice made by those who lost their lives.
Speaking outside Glasgow Cathedral ahead of a service of commemoration for Commonwealth leaders, the Prime Minister said it was important to find new ways of bringing the experiences of those involved in the conflict to life.
It was an extraordinary day in Britain's history, and when you think that almost every family, almost every community was affected... Almost a million British people were lost in this war, it's right that almost a hundred years on we commemorate it, we think about it and we mark it properly.
He also told BBC Breakfast: "I think it is important to remember the outbreak of the war.
"Because although there was an enormous amount of waste and loss of life, there was a cause that young men rallied to at the beginning of the war, which was the idea that Europe shouldn't be dominated by one power, that a country, a small country like Belgium shouldn't be simply snuffed out."
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.