File:Fort Lingan 6-inch Gun Breech.jpg

Fort Lingan 6-inch Mark 7 Gun with breech open.

6-inch guns were one of the stalwarts of British coast defence ever since the first marks appeared during the early 1880s on a variety of barbette and disappearing carriages, but when the Mark 7 appeared in 1898 it gradually replaced all the earlier models. Produced in greater numbers than any other of a bewildering array of 6-inch gun marks and sub-marks, the Mark 7 was deployed all around the world on four marks of pedestal mounting.