WWII: Did Aliens Save Britain?

They stand like alien creatures from H.G.Wells' War Of The Worlds, silent sentinels in the Thames and Mersey estuaries...wartime defences such as I'd never seen until recently.

image by Diamond Geezer/Flickr

I found this picture on-line and felt compelled to find out more.
In the darkest days of the Second World War, Britain stiffened its upper lip and came up with numerous strange but hopefully effective ways to defend itself (the Dambusters' 'bouncing bomb'; Mulberry harbours; radar; the fiery coastal pipeline system)...
After France fell, the Germans were regularly hitting Allied shipping in the English Channel, and enemy planes were bombing London Docks without much resistance. The Admiralty sought out designer Guy Maunsell - his idea became known as the Maunsell Sea Forts. The Thames and Mersey waterways were vital for transporting much-needed food and equipment, and these forts (three in the Mersey, four in the Thames) were designed to protect UK's most important ports, London and Liverpool.
The towers were built in 1942. Interconnected steel platforms held anti-aircraft weaponry; one tower was for accomodation and control; another housed a powerful searchlight. To get an idea of scale, note the two floors of windows.
My first thought was: were they worth it? Well, it seems the forts shot down 22 aircraft and about 30 flying bombs, so they proved of value (though it may have been cheaper to have bought a few more squadrons of Spitfires!).
The forts were decommissioned in the 1950s, due to deterioration and a collision (by Norwegian ship Baalbek in 1953, which destroyed two towers, killed four civilian caretakers and destroyed guns, radar equipment and supplies).
So, what to do with them once their military usefulness was over? Post-war, they've been used for a variety of activities, such as pirate radio in the 1960s and the establishment of the self-styled Principality of Sealand in the same decade. Their designs were used extensively in the development of drilling platforms and offshore fuel exploration. They were the blueprint for the very first offshore oil platform (in the Gulf of Mexico) before 1950. For this very reason alone they have immense historical significance. Since 2003, serious talks have been held between concerned parties and the UK Govt to try and preserve them.
England saw off Hitler many years ago. Hopefully these remarkable sea forts can fend off time and rust in the same successful manner.

UPDATE: 29 May 2015 - An intriguing plan to turn the old sea forts into a luxury resort!