At 3: 10 A.M. on June 7, after a week of bombardment by the heaviest concentration of artillery seen on any front up to that time (Plumer had a gun for every seven yards of front), the mines were detonated. All nineteen went off nearly simultaneously, sending the entire ridge into the air. Tremors were felt in London—Lloyd George himself heard a faint boom while working through the night at 10 Downing Street.
