In response to questions at a conference, Dr Williams described how strong the impact of the Mass was on him. "I found myself that evening kneeling at prayer in tears and feeling that I'd been taken somewhere new.

"I had to change, I had to grow, I had to repent. I had to let that reality become more real for me," he said. The future leader of the Church of England and primus inter pares of the Anglican Communion grew up in a Christian household but started out with his family in the dominant Welsh non-conformist Presbyterian tradition.

When he was 11 the family moved and became members of the Anglican Church in Wales. Welsh Anglicans, particularly in South Wales, have long a tradition of "high" Anglo-Catholic worship.

To a highly intelligent, devout teenage boy, however, even their elaborate incense-perfumed rituals would have seemed tame by comparison with the three-hour Divine Liturgy of St John Chrysostom as celebrated weekly in Orthodox churches worldwide.

Dr Williams said: "When I came away, I felt I had seen glory and praise for the first time. I felt I had seen and heard people who were behaving as if God were real."

"I came away with the sense of absolute objectivity and majesty and beauty of God which I have never forgotten. If people worshipped like this, I felt God must be a great deal more real (than) even I have learnt him so far."

The other epiphany was at the other end of the theological spectrum, in a Baptist church three years later.

He spoke about his teenage encounters with God when he was addressing a meeting in Egypt of bishops and archbishops from the Global South, the grouping of conservative evangelical provinces in Africa, Asia and the West Indies which regards itself as carrying the Orthodox flag in the Anglican Church today.

The meeting was private, but the question and answer session was made public yesterday when Global South organisers posted it on their website.

Dr Williams also described how he had helped to convert three people to Christianity, including Gwyneth Lewis, the national poet of Wales, who he said came knocking on his front door ten years ago after years of involvement in Buddhist meditation.

After about two years, she was confirmed as an Anglican, the Archbishop said.

The Orthodox Church in Britain was boosted after 1992 by an influx of former Anglicans opposed to the ordination of women. The Archbishop also said that Christians needed to be sensitive when communicating with Muslims.

"While we cannot accept Islam as the final revelation, it is nonetheless possible that God has given great gifts to individual Muslims and that through their devotion, we may yet learn something of what obedience to God looks like."

Russian Orthodox

Part of the family of Orthodox Church that developed from church of Byzantine Empire. Lasting schism with Rome in 1054 Claims 80 million followers; detractors say closer to 40 million. One of 14 patriarchates or churches, plus several autonomous churches that honour primacy of Patriarch of Constantinople Church of England

Celtic Church gave way to Roman Church at Synod of Whitby in 664. Schism with Rome came in 16th century Million regular communicants, 25 million baptised One of 38 provinces of the Anglican Communion, all in full or "impaired" communion, acknowledge Archbishop of Canterbury as primus inter pares

www.timesonline.co.uk/faith Ruth Gledhill's weblog

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