In 1951, he transferred to the Pan-Cypriot Gymnasium, Nicosia, having become a [[monk|rasophore]], and he was later [[ordination|ordained]] [[deacon]] on the Sunday of [[Pentecost]], 1953, at the Church of St. Sava in Nicosia by the late [[Archbishop]] [[Makarios III (Mouskos) of Cyprus|Makarios III]]. He graduated from the Gymnasium in 1954 and went to Athens to study at the Theological School of the University. Before receiving his university degree in February 1959, he was appointed to the Church of All Saints in London. He arrived there and started his duties at the Church of the Holy Saints in Camden Town in April 1959. He was ordained [[presbyter]] by the late Archbishop of Thyateira, Athenagoras (Kawadas), on the [[April 26]] of the same year.

On [[April 16]], 1988 he was unanimously elected by the Sacred Synod of the Ecumenical Patriarchate as ''Archbishop of Thyateira and Great Britain'' and his [[enthronement]] took place at the Cathedral of Sophia in West London. His tireless program saw him attending many community events, both in London and around the country. His quiet and reasoned voice upholds both the concerns of the Greek Orthodox community and expresses the Christian message of peace and reconciliation. During the Kosovo conflict, in 1999, between the local Albanians and the Serbian army where NATO forces intervened, he was interviewed on BBC radio. Through his questions, the journalist appeared keen for Gregorios to side with the (fellow) Orthodox Serbs and criticize NATO. His Eminence simply stated that it was time for reconciliation and especially a time "of repentance for all of us."