The V1 and V2 rockets were developed as a reaction to the heavy allied bombing of German cities towards the end of WW2. (V stands for Vergeltungswaffe - retribution weapon'). In total, over 3,000 V2s were launched against Britain, resulting in an estimated 9,000 deaths.
V1s, known as doodlebugs, flew until they ran out of fuel and then they dropped to the ground. So people on the ground would listen hoping to hear it pass overhead, but if the noise stopped while it was still coming towards them they would dive for cover. The V2s were the world's first long-range guided ballistic missile and as such no one heard them coming.
2018: A London Inheritance has a great post about V2s.
2018: "Drone Warfare: The Development of Unmanned Aerial Conflict" by Dave Sloggett, references "Most Secret War" by R. V. Jones where Tower Bridge is named as the permanent target for all the London V1 rockets. It seems to be generally agreed that the V1s were not at all accurate and many fell short.
2019: LRB has an interesting post about these bombs, particularly in the the comments about their random nature.