The Martello Tower at Hackness in Longhope, South Walls is one of Orkney's hiddens gems, if you can count something as hidden if it's 33 foot high with a huge gun on the top of it that is!
It's hidden in the sense that not a lot of people visit the site, in fact our tours make up around 10% of the site's total visitor numbers in a year - quite impressive when we only go once a week with eight people. Part of the problem is that you have to take a ferry to get there, but a then a lot of folk don't think they'll like it so don't bother. Our most common comment from guests is along the lines of they wouldn't have visited if on their own, but are really glad they went.
Most Martello Towers were built on the south coast of England to repel prospective Napoleonic invasion, Hackness (along with a gun battery and barracks, which we also visit) and its paired tower at Crockness were built to protect against American privateers during the war of 1812, when convoys for the war effort gathered in Longhope Bay. The war only lasted to 815 and neither the towers or the battery ever fired a shot in anger.
The gun on the top today isn't the original, which was a 68 pounder added when the defences were upgraded in in 1866, but it is a genuine 64 pound Armstrong semi recoilless gun, found in the Caledonian canal, where it was being used as a mooring point.
Martello towers aren't a British invention, they're based on a 16th century Genoese tower at Mortella in Corsica, part of a series of coastal defences built to defend Genoa's trade against Barbary pirates. The original Torra di Mortella was occupied by the French and used to defend the bay against the British, and successfully withstood attack by HMS Juno and Fortitude in 1794, eventually being taken by land assault. The army officers were impressed and made detailed plans of the tower and its armaments, which are pretty good works of art in their own right:
Others must've thought so too, as prints of the original were made and sold at the time, and it must have been a well-known action that got a lot of publicity. You can see a lot of the features that were later incorporated in the later British design, but the big flaw in the original Martella tower was that its main armament, the two 24 pound guns, could only fire forward out to sea, and its rear was protected by just one 6 pounder, hence vulnerable to attack from the landward side:
This was remedied in the subsequent design, with a 360 degree arc of fire for the one gun on the top, but in true British fashion we got the name wrong and it became Martello instead of Mortella. We also blew the original up when we left - tactical necessity at the time but a great shame now:
The attacks are all documented in the London Gazette for 1794, and contain a description of the original attack and the damage inflicted:
'In Obedience to your Orders, I went Yesterday in His Majesty's Ship Fortitude, which I command, against the Tower of Mortella, where I remained Two Hours and a Half; when finding that neither the Fire of the Fortitude nor that of the Juno (who was extremely well placed to batter the Tower) had made any material Impression; and the Main-Mast of the Ship being much wounded, many of the Shrowds cut away, Three of the Lower Deck Guns dismounted, several hot Shot in the Hull, and a great many Men blown up by the Explosion of Powder from a Powder-Box that was struck by a hot Shot; and being so near the Tower and the Rocks, that if the Wind should die away it would be difficult, and if it should change so as to blow on Shore it might be impossible, to get away, I thought it prudent to haul off. Soon after I had done so, the Ship was perceived to be on Fire from the Main Deck to the upper Part of the Quick Work on the Quarter Deck, occasioned by a hot Shot that had lodged in the Side; but after cutting out the Shot, and opening the Side in different Places, the Fire was extinguished without having done any material Damage'.