It’s 77 years since D-Day but it might never have happened at all without one very specific piece of new technology; the resonant cavity magnetron. Atomic bombs or the Colossus supercomputer may come to mind when thinking about innovations which changed the course of WW2, but without this technological breakthrough, history would have been very different. Historian Norm Fine talks to James about the development which enabled microwave radar, and why he thinks it was the single most influential new invention which eventually won the war.

You can read more in Norman Fine’s book, Blind Bombing: How Microwave Radar Brought the Allies to D-Day and Victory in World, which is out now.