When you think about the bombing of the UK during the Second World War, many initially think of the Blitz and the use of horrific terror weapons such as the V1 and V2 rockets. Yet in the north too, towns and cities suffered from similarly-terrifying air-raids. One such city was Grimsby, situated on the southern bank of the Humber estuary. In 1943 the residents of Grimsby and Cleethorpes became the victims of a new type of morale-wrecking weapon: the butterfly bomb - history's first ever cluster explosive. Drones historian James Rogers tells the story behind the butterfly bomb: why it was such a deadly weapon of war and how the local residents of Grimsby and the surrounding area pulled together to deal with this new threat.