By Luke Weir & Sam Elliott-Gibbs These eye-opening towers standing deep in the ocean were built to protect the UK against a Nazi invasion, but to those seeing them for the first time, you’d be forgiven for thinking you were on the set of a new alien-themed film. The remarkable structures wouldn’t look out of place rushing out of the water in a sci-fi thriller, like the walking extra-terrestrial tripods depicted in War of the Worlds. In fact, the creation had a short-lived – but important use – and who knows where we would be without them? The Maunsell Forts were originally built in 1942 to hel…