![How One Girl’s “STUPID” Chalk Trick Made German U-Boats Sink 3 Times Faster - YouTube [34:33]](https://rdl.ink/render/https%3A%2F%2Fi.ytimg.com%2Fvi%2F_LDE9z9ZQiE%2Fmaxresdefault.jpg?width=92&height=&ar=&mode=&format=avif&dpr=2)
How One Girl’s “STUPID” Chalk Trick Made German U-Boats Sink 3 Times Faster - YouTube [34:33]
March 1943 – Derby House, Liverpool.Nineteen-year-old Janet Patricia Okell stood over a chalk-marked floor in the freezing basement of the Western Approaches...