Grant met Aleister Crowley in 1944 and was initiated into the A.'.A.'. in 1946. According to occult historian P.R. Koenig, Crowley called Grant "a definite gift from the Gods", but a careful reading of this citation show Crowley was praising Grant's work as a secretary. In March 1946, Crowley wrote in his diary: "Value of Grant: if I die or go to U.S.A., there must be a trained man to take care of the English O.T.O."
After Crowley's death, Grant's was issued a IX° charter in O.T.O by Crowley's successor, Karl Germer, in 1948; and received authorisation to form an O.T.O. Camp in England in 1951. In 1952, he wrote a new manifesto for his group and had 5000 copies printed.
In 1954, Grant began the work of founding the New Isis Lodge. The lodge became operational in April 1955 when Grant issued a manifesto announcing his discovery of a "Sirius/Set current" upon which the lodge was to be based. Karl Germer was so displeased with this manifesto that on July 20, 1955, he issued a "Note of Expulsion" expelling Grant from O.T.O., and naming Noel Fitzgerald as the leader of the British section of the Order
Nevertheless, Grant claimed for himself the title O.H.O. (Outer Head of the Order) of Ordo Templi Orientis. The branch under the leadership of Grant was commonly called the "Typhonian" Ordo Templi Orientis, but is now officially named the Typhonian Order. The
New Isis Lodge was absorbed into Grant's Order in 1962.
Members of Grant's Ordo Templi Orientis in the past have considered him the rightful O.H.O. of O.T.O, as evidenced by this quote from a 1976 edition of
Sothis magazine:
Karl J. Germer, having proved himself blind to the implication of Crowley's letter to him, failed to understand and accept when — soon after Crowley's death — Grant submitted his plans for change... It remains to remind those who support the old-aeon concept of the O.T.O. that they have not produced — nor can they ever produce — the slightest evidence of a creative current in any of its forms.