Beneath the waves in the Thames Estuary lies the wreck of US Liberty ship the SS RICHARD MONTGOMERY, less than 200 yards from a busy shipping lane and little more than a mile from the low-lying shores of Kent and Essex. But this is no ordinary wreck. With the masts eerily visible, the ship is stuck irretrievably on sandbanks. Its cargo contains a sinister cache – over 3,000 tons of WWII explosives – time bombs waiting to explode.