Source: http://www.bbc.com/future/story/20140905...

Although there is no exact figure, estimates suggest that several thousand people were killed by the missile – 2,724 in Britain alone. However, a far grimmer statistic is that many more, at least 20,000, died constructing the V2s themselves.

“It’s something that’s often glossed over, but shouldn’t be,” says Doug Millard, space historian and curator of space technology at London’s Science Museum, where a V2 takes pride of place in the main exhibition hall. “The V2 programme was hugely expensive in terms of lives, with the Nazis using slave labour to manufacture these rockets.”