Prime Minister David Cameron was among many across Britain who commemorated the centenary of the First World War by switching off the lights at Downing Street this evening.

A single candle was left burning on the doorstep of Number 10 as a symbol of remembrance of those who died in the war.

LIGHTS OUT – One Million Candles to Remember, was a national project initiated by The Royal British Legion, encouraging people around the country to switch off all household lights and light a single candle between 10 and 11pm.

The project was inspired by the words of Sir Edward Grey, then British foreign secretary, on the eve of war. He said: "The lights are going out all over Europe, we shall not see them lighted again in our lifetime."

Westminster Abbey joined in the commemorations by holding a vigil, which included music, scripture and contemporary readings. Towards the end of the vigil, the Abbey moved from light to darkness, leaving a single candle burning by the grave of the unknown warrior, until that too was extinguished at 11pm.