During an interview with Charles Moore of The Daily Telegraph at Lambeth Palace, London, he was asked by Moore that since he was an evangelical, could he speak "in tongues" which the journalist said is the "charismatic" spiritual gift recorded in the New Testament.
Moore said that Welby answered "Oh yes", as if he had been asked if he plays tennis.
"It's just a routine part of spiritual discipline - you choose to speak and you speak a language that you don't know. It just comes," the Archbishop said.
Moore said he first saw this man 40 years ago, when they were both pupils at Eton, a top British independent boarding school located in Eton, near Windsor in England.
"Later, I was with him at Trinity College, Cambridge," Moore went on to say. "He was the shyest, most unhappy-looking boy you could imagine. Now he is 105th in the line that began with St Augustine. He seems to be loving it.
"I remark on the change, and he agrees. 'That's something to do with the Christian faith,' he says."
Moore then asked if it was necessary for a true Christian to have a personal conversion experience.
The Archbishop then told him: "Absolutely not. There is an incredible range of ways in which the Spirit works. It doesn't matter how you get there. It really does quite matter where you are."
Moore asked if it was like "suddenly realising that you love someone and want to marry that person?"
The Archbishop laughed and told him, "That's not what happened with Caroline [his wife] and me! And it's not what happened with Peter, who got engaged to a lovely girl two days ago. That's been a gradual thing."
Moore went on to say that it did happen to him, in New Court, Trinity College, during the evening of October 12, 1975. At Eton, he had "vaguely assumed there was a God. But I didn't believe. I wasn't interested at all."
He said that night in Cambridge, though, praying with a Christian friend, he suddenly felt "a clear sense of something changing, the presence of something that had not been there before in my life."
Welby then said to his friend, "Please don't tell anyone about this", adding, "because I was desperately embarrassed that this had happened to me, like getting measles."
Moore said, "Since then, there have been long periods with 'no sense of any presence at all', but he has never gone back on that night's 'decision to follow Christ'. This is not his doing: 'its grace. Grace is a reality: feelings are ephemeral.'"
He concluded by saying, "All the time, this active, wounded, happy man is trying to find new ways in which this country, despite the secular age, can give its allegiance to God."
Source: ASSIST News Service