It was similar but unrelated to the 12-inch siege howitzers Mk II and IV.

The longer-barrelled Mk III soon followed, with a heavier breech to balance the gun.

Mk V, dating from July 1917, moved the recoil buffer and recuperator into a single housing below the barrel, which was common for all new British artillery developed during World War I.

[2] Mk V also relocated the loading platform from the railway wagon to the revolving gun mounting, which now allowed 120° of traverse, and by overhanging the opposite side provided crew access when the gun fired to the side (90° traverse) and also helped to balance it.

[2] All 3 versions served on the Western Front in World War I, usually in 2-gun batteries, operated by the Royal Garrison Artillery.