“The Battle of Britain” usually refers to the German bombing campaign during the summer of 1940, planned to lead into a seaborne invasion across the English Channel.
Gerald Gardner claimed that the “Southern Coven” performed a ritual in the New Forest at Lammas 1940 against the threatened invasion. Based on my reading of the evidence, or lack thereof, I don’t think that this ritual took place as he described it.
Nevertheless, telling about the ritual fifteen years after it supposedly happened was part of his claim that Wicca was an indigenous British religion that could repel the “foreign invader,” Christianity. (And if alive today, Gardner would probably add Islam as well to the list of invaders.)
Whereas we have only Gardner’s after-the-fact claim that the Lammas 1940 ritual occurred, another esoteric group was indeed fighting Nazi Germany on the astral plane—Dion Fortune’s Fraternity of the Inner Light.
“The Magical Battle of Britain,” by Dave Evans and David Sutton, is available at The Fortean Times.
The authors describe how Fortune’s group conceived of their magical battle, designed to strengthen British will power and stop the invasion, even if its effects are hard to quantify compared to those of the Royal Navy, the Royal Air Force, and the Army.
Some of her followers believe that the workings ruined her health, leading to her death a few years later.
And they quote a well-known scholar of esotericsm who comes to this conclusion:
Possibly such tales of magical warfare are simply one of the ways, as esoteric scholar Professor Wouter Hanegraaff describes, in “which magicians seek to legitimate magic to the wider society as well as to themselves” in the modern era.