In Lufwaffe raids the bombers had formidable protection from night fighters and there was an urgent need to find a way of giving our defending fighters a better chance against them. Britain was ahead in the radar race and the idea was conceived to miniaturise radar sets to be small and robust enough to be carried on our own night fighters. A downward-looking radar system called “H2S” was already in use in bombers, which gave some rough view of the ground through cloud cover.