Following the success of their BL 9.2-inch howitzer, Vickers designed an almost identical version scaled up to a calibre of 12 inches, the Mk II entering service on the Western Front in August 1916.

[2] Eight complete equipments are reported as arriving in August 1916 and being in action in France shortly afterwards.

It was similar but unrelated to the BL 12-inch railway howitzers Mk I, III and V produced by the Elswick Ordnance Company at the same time.

As with other large-calibre weapons, it was operated by the Royal Garrison Artillery in World War I.

It was then reassembled on its static siege mounting on top of a steel holdfast, with 22 tons of earth in a box sitting on the front of the holdfast in front of the gun, to counteract the kick of firing.