The pedestal mounting and the gun crew were enclosed to the front, sides and top in a reinforced-steel barbette.

The first UK installation was at Eastern Arm Battery in Dover, just before the outbreak of World War II.

[3] The pair installed in 1944 at Fort Rodd Hill at Esquimalt Harbour, British Columbia, may be the last in existence.

These would lie in wait for convoys and then, at the appropriate moment, sweep across their front, firing torpedoes and making a speedy escape into the darkness.

Along with these four, three of the Admiralty type flotilla leaders, HMS Campbell, Mackay and Montrose, were refitted with the mount.