A welcome return for "Guy in the Sky", who gave us a brilliant talk on Concorde last year.

As Britain faced the threat of Nazi invasion it became clear our airforce was outnumbered 4:1. The British Government turned to scientists for a solution. They asked for a Death Ray - what they got was even more advantageous. The story of how two unlikely men and a mathematical formula changed the tide of the war. They say truth is stranger than fiction. Indeed, it was here.