This Day in History: February 6th, 1756 the King of England called the nation to a day of “solemn prayer and fasting” because of the threatened invasion by the French. “The fast day was a glorious day, such as London has scarcely seen since the restoration. Every church in the city was more than full, and a solemn seriousness sat on every face. Surely God heareth prayer, and there will yet be a lengthening of our tranquility.” ~ John Wesley’s journal. BTW: The French did not invade.
Sources: Christian History Magazine & http://watchmanmedia.org/index.php/2016/07/27/britains-history-was-shaped-through-prayer-fasting/