the guns arrived with their carriages in france on 26 may 1918, but incomplete, and were not in action until 8 august. the two guns were operated by 471 siege battery from may 1918, and were known as "hm gun boche buster", operating near arras with first army, and "hm gun scene shifter", operating near bethune with fifth army. they were used for long-range interdiction fire on key german targets such as railway junctions. king george v personally oversaw the firing of the first shell by boche buster from near marœuil, 6 km nw of arras, on 8 august in a fireplan to hit german reinforcements being sent south to oppose the british amiens offensive. this shell heavily damaged a railway junction at douai and became known as "the king's shot". a total of approximately 235 rounds were fired by the guns during their four months on the western front.