Beginning in the 1960s, the teaching of British Israelism was vigorously promoted by Herbert W. Armstrong, founder and former Pastor General of the Worldwide Church of God. Armstrong believed that the teaching was a key to understanding biblical prophecy: "One might ask, were not biblical prophecies closed and sealed? Indeed they were—until now! And even now they can be understood only by those who possess the master key to unlock them." Armstrong believed that he was called by God to proclaim the prophecies to the Lost Tribes of Israel before the "end-times". Armstrong's belief caused his separation from the Church of God Seventh Day because of its refusal to adopt the teaching.