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.
Princes William and Harry and the Duchess of Cambridge paid a visit to the Tower of London today as part of the commemoration of the First World War centenary.
The trio chatted to staff and the famous Beefeaters at the site, which is one of London's oldest buildings.
The grounds of the tower were specially covered with poppies to commemorate 100 years since the beginning of the conflict that claimed over 1 million British lives.
The Tower was one of a number of famous monuments that turned out their lights to mark the centenary.
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.