Listing Text

PORTLAND

SY67SE PORTLAND HARBOUR, H.M. Naval Base
969-1/1/158 Breakwater Fort
21/09/78

GV II

Breakwater fort. c1860, but considerably modified and extended
in 1884, 1900, 1912 and later. Portland stone, concrete,
armour-plate steel. Locally known as "Palmerston's Folly",
this was one of 4 coastal defence forts provided, others being
at Plymouth and Spithead. Later armaments added in both World
Wars.A small jetty running to the SW is formed over 3
segmental arches with quoins and keystones, approached by a
slow- rising long staircase/ramp, left, and a steeper flight
of stairs to the right; extends also to left, including
unroofed 3-bay stone structure. Main fort includes 35m
diameter iron core with foundations c 9m below sea level; a
ring of masonry capped with concrete on granite sub-structure
c 7m above sea level. The iron structure has 2 rings of iron
box girders fanning from central well, forming a floor and a
roof level; concave fluted underside sloping to gunports,
supported by pillars between casemate ports. Walls are three
thicknesses of 15cm plate backed by armour bars; roof also of
concrete-capped iron. 14 guns installed 1874-75. In 1884 a
steam engine was added to supply ammunition and operate the
guns. Upper level altered by installation in 1900 of 2 heavy
gun emplacements, and later by substitution of an armoured gun
tower for the original lantern. Central well is octagonal
faced with ashlar and with Roach stone rustication to each
arched entry; spiral cast-iron staircase to upper level.

Listing NGR: SY7077376223