The late Prince Philip, God rest him, had no Greek blood. He was rather a typical representative of the descendants of Germanic princes who were sent, mainly by Great Britain, to be constitutional monarchs in Eastern Europe in the 19th century. This was in order to spread British Imperial control and prevent Russian princes taking their places in newly freed countries there. As his family had been sent from what is now Germany to Greece, he therefore nominally became Greek Orthodox.
However, Philip never seems to have practised this Faith at any point and when he married Princess Elizabeth, he nominally became a member of the Church of England. In reality, this did not mean anything as the Church of England has no method for receiving Greek Orthodox. Many children of nominal Greek Orthodox parents who immigrated here after 1945, having lost their knowledge of the Greek language and Greek ghetto culture and been assimilated, have done the same thing. Indeed, I can number twelve Anglican ministers who are of Greek and Cypriot origin in just this part of England.
Technically, therefore the late Prince Philip was an apostate. However, since he never practised Greek Orthodoxy, does this mean anything? True, in 1992 he did talk about religion to some Orthodox bishops, including the late Parisian Metropolitan Antony Bloom and he is alleged by some to have received communion from him. However, the religious views expressed by the late Prince both before and since then appear to have nothing Orthodox about them at all. They express rather the apostate views of those who believe in some vague Deity and the universality of religion. Certainly he was not a practising Orthodox Christian, but a syncretist who thought that all that religion could tell us is that there is some ‘Divine force’ in the Universe.