HMS Belfast is one of only three remaining vessels from the bombardment fleet which supported the Normandy landings on 6 June 1944. But two years before D-Day and Operation Overlord, the Allies mounted a daring rehearsal raid on the French port of Dieppe. The attack ended in disaster, but out of its ashes came one of the greatest unsung inventions of the Second World War, one that would keep the Allies in the fight when they returned to invade Normandy. Find out about the Mulberry Harbours in th