The Germans during WW2 had a project to have a 25-barrel HDP-V3(high pressure pump - vengance weapon 3) battery constructed between Calais and Boulogne on the channel coast in 1943; to enable direct firing on London roughtly 95 miles away;the weapon was expected to be fired at a rate of approximately 200 shells an hour.

617 squadron RAF raided the site in 1944 and one 'Tallboy' bomb destroyed the underground facilties.

Regards.
CD