A spy there under our very roof was our babysitter, Klaus Fuchs. He would come and take care of my sister and me, and since we were five and eight, we did not need much looking after. But we had a piano in the house and he loved to play the piano, so that was our babysitter. Then, when I got a little older, I was actually Peter Oppenheimer’s babysitter. I mean, you should not really trust a ten-year-old to babysit, but you know, with a guard walking around outside, what could go wrong?
From the interview: