The war had started 3 years ago. Life was hard, especially in areas that were heavily bombed. In every house, there was a shelter either inside or in the back garden that you had to go into if there was a bomb being dropped. The sky was usually lit up by smoke, which meant it was harder to breathe, meaning you had to stay inside.
Germans were bombing London heavily at this point and no one could see anything through the smoke. There were evacuations to leave London. The Germans knew that the evacuations were happening and waited which meant that in the beginning, it was all a trap.