Edward Alexander Crowley was born on 12 October 1875 to a well-off family of Plymouth Brethren in Leamington Spa. He was a wilful child, and his mother nicknamed him Therion, the Great Beast 666, from the Book of Revelation.
After school, Crowley went to Trinity College, Cambridge, to read natural sciences. He devoted little time on his studies, and excelled instead at chess and mountaineering. At 22, he decided all was worthless except magic and the occult. He changed his name to the Celtic-sounding Aleister, and spent his spare time writing poetry.
He left Cambridge with no degree and moved to London, where he joined the Hermetic Order of the Golden Dawn. There he met and fell out with the poet W B Yeats, who memorably described Crowley as “an unspeakably mad person”.