Most Secret War

by R.V. Jones

We had a new and enthusiastic physics master who set us more homework than I could manage; and at the end of more than two hours when the supposed allocation was 45 minutes, I had to solve a problem in specific heats. I worked the answer out to thirteen places of decimals, knowing perfectly well that this was quite unjustified, and in fact getting the answer wrong. The master promptly sent for me, saying that surely I knew better than to work out an answer to that degree of meaningless precision. I replied that I did, but that I thought he would like an answer matching the length of the homework that he had set us. The result was that he moderated his demands, but the point of the story in this context is that as fourth form schoolboys we already well knew how many places of decimals were justified in particular measurements: its significance was to be evident at Coventry in 1940.