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One hundred years have now passed since Britain went to war with Germany.

The man who played a pivotal role in that decision was the Foreign Secretary of the time, Sir Edward Grey.

It fell to him to go to the House of Commons and argue the case for war -- something that would have been made all the more difficult by his personal hatred of war, and the role he was forced to play.

Senior historian Dr Richard Smith took Richard Bacon to the very room in the Foreign Office in which Sir Edward Grey made the decision, and uttered his famous line "the lamps are going out all over Europe".

This clip is originally from Richard Bacon on Monday 4 July 2014.