Large numbers of blips moving across the Channel prompted red alerts – but had an innocent explanation
On 20 March 1941, RAF Fighter Command sounded a red alert. The Chain Home radar had detected a large number of blips moving across the Channel and it looked like a mass Luftwaffe bomber raid was on the way. But 40 miles from the south coast the blips faded out to nothing, and no aircraft were sighted.
The same thing happened several times, with fighters scrambled to intercept intruders only to fail to find any. The spurious radar tracks were whimsically known as “angels”, and radar technicians suspected they were caused by weather conditions.