Guernsey and its neighbouring islands have a unique distinction which sets them apart from the rest of the British Isles. Together with the rest of the Channel Islands, they were the only part of the British Isles to fall to Nazi Germany in the Second World War. In this documentary, Dan Snow discovers the unique wartime experience of these islands and the people who lived on them. From a daring commando raid on Sark to an extraordinary reconnoitre of untouched World War Two archaeology submerged in an Alderney quarry, join Dan as he explores the wartime history - above and below the ground.