Work began on the Gosport Lines in 1678 and when the circuit was completed consisted of a rampart 10-11 ft high without a parapet and a moat, partly wet and partly dry, 30 ft wide and 11 ft deep. It was unfinished at the time of Charles II’s visit in September 1683 and despite adverse comments in official reports deteriorated further during the early C 18.
In 1748 the rebuilding of the Lines began and was to continue for half a century. Between 1751 and 1752 all but the southernmost curtain had been rebuilt and enlarged and the construction of a covered way and glacis beyond was envisaged.
The next phase began in 1757 with a covered way and glacis outside the moat on the southwestern side, and a new rampart and moat was constructed from the north angle of the main central bastion roughly parallel to the line of Weevil Lane down to Forton Lake. The Lines were extended beyond Forton Lake to enclose Priddy’s Hard, presumbably to prevent an enemy occupying the area and bombarding the dock. The RNAD built the Great Magazine there c 1770.
The Weevil Lane part of the defences was given a moat, covered way and glacis following the French invasion threat of 1779. The Priddy Hard Lines were also enmoated at this time. The final major construction work involved upgrading the section from the Canoe Lake to the mouth of Haslar Lake, between 1797 and 1802. The land here was owned by the Bishopric of Winchester and for some 20 years a legal wrangle had ensued, preventing the upgrading of the Lines. The new section ended in a corner bastion mounting 14 gun positions.
The lines were completed with the addition of Ravelins between the bastions, during the C 19. With the defeat of Napoleon and the stated policy of using the Navy as Britain’s “Wooden Wall”, the fortification became redundant. At the express wish of Queen Victoria, the railway was extended from Gosport station to the pier at Royal Clarence Yard in 1845, thus breaching the Lines. Walpole Road had been driven through the lines by 1890, and spasmodic demolition has continued ever since.