Homeowners across the Sid Valley extinguished their lights in the lead up to the moment, exactly 100 years ago, that Britain declared war on Germany.

They joined a country-wide commemoration, leaving only a single candle lit in each house between 10pm and 11pm on Monday.

The moment of shared reflection was organised by 14-18 Now, the official cultural programme for the World War One centenary commemoration.

Sidmouth Town Council chairman John Hollick, who joined in, said: “It was different and another way of making people aware.

“I hope that people did observe, and those who didn’t still appreciate why it was done.”

More than 140 explorer scouts and leaders from across Devon carried lights to the top of the ten tors on Dartmoor and extinguished them at 11pm. East Devon’s Axe Air Explorers then camped out in the wind and rain.

Will Grant, 17, said: “It was very moving. From Laughter Tor, we could see six of the other tors and we could see when all the lights went out.

“It makes you think that someone of my age could have gone to war and never come back.”

Inspiration for ‘Lights Out’ came from a famous remark made on the eve of the outbreak of war by the then Foreign Secretary, Sir Edward Grey, who said: “The lamps are going out all over Europe; we shall not see them lit again in our lifetime.”

Britain declared war on Germany at 11pm on August 4, 1914, ushering in one of the darkest periods in the country’s history.

Jenny Waldman, the director of 14-18 Now, said: “I would like to thank all those who took part in Lights Out across the UK and helped to make it such a moving and fitting tribute to those who gave their lives in World War One.”

The organisers credited it as one of the most dramatic UK-wide events ever staged.