With its formidable firepower, its main purpose was to guard the approach from potential landing areas on the south Hampshire coast.

Forts Brockhurst, Grange and Rowner were designed on the plan of a detached bastion with an obtuse salient.

They were intended as bastions affording each other mutual support but, as the ditches of one could not be flanked by the other, caponiers were necessary at the angles.

The work was taken over by the Royal Engineers and completed using military labour at a cost of £1,561 to correct the faults.

[2] A feature of the three new Gosport Advanced Line forts was the circular keep placed centrally to the rear.

It was still argued in military circles that a keep, although considered by some to be an unnecessary hang-over from the medieval period, was still needed to protect the unfortunate survivors of a fort that had been overrun by the enemy from the overzealous excesses of a victorious army.

The site plan for the Gosport Advanced Forts lists the following armament :- Redoubt and Haxo 11 x 8-inch S.B.

[1] The fort was manned by companies from the Royal Garrison Artillery and in the 1880s it became the Depot of the 2nd Brigade Southern Division R.G.A.

Rowner was heavily overgrown for many years until the Navy, at a cost of £400,000, cleared its ramparts and the roof of the keep in 1994.