Re: guess what is missing 4
It is a martello tower at the head of Sovereign Harbour Eastbourne
https://en.wikipedia.org/wiki/Martello_tower
Between 1804 and 1812 the British authorities built a chain of towers based on the original Mortella tower to defend the south and east coast of England, Ireland, Jersey and Guernsey to guard against possible invasion from France, then under the rule of Napoleon I. A total of 103[5] Martello towers were built in England, set at regular intervals along the coast from Seaford, Sussex, to Aldeburgh, Suffolk. Most were constructed under the direction of General William Twiss (1745–1827) and a Captain Ford.[9][10] The northernmost tower at Aldeburgh is of quatrefoil design, i.e. four in one.[11]
Included in the scheme were three much larger circular forts or redoubts that were constructed at Harwich, Dymchurch and Eastbourne; they acted as supply depots for the smaller towers as well as being powerful fortifications in their own right.[12]
The effectiveness of Britain's Martello towers was never actually tested in combat against a Napoleonic invasion fleet. They were, however, effective in hindering smuggling.[13] After the threat had passed, the Martello towers in England met a variety of fates. The Coastguard took over many to aid in the fight against smuggling.
A Martello tower at Clacton-on-Sea on the east coast of England.
Fifteen towers were demolished to enable the re-use of their masonry. The sea washed thirty away and the military destroyed four in experiments to test the effectiveness of the new rifled artillery. During the Second World War, some Martello towers returned to military service as observation platforms and firing platforms for anti-aircraft artillery.
Forty-seven Martello towers have survived in England, a few of which have been restored and transformed into museums (e.g., the towers at St Osyth and Seaford) visitor centres, and galleries (such as Jaywick Martello Tower). Some are privately owned or are private residences,[14] The remainder are derelict. A survey of the East Coast towers in 2007 found of the 17 remaining, most were in a reasonable condition.[15]
Many remaining Martello Towers are now Listed Buildings.[16]