But now the grown men who were victims of the abuse as boys are coming forward to challenge the archbishop's version of events, casting doubt on his claims of ignorance.

The archbishop, 61, was working abroad in 1982, when an internal investigation by an influential Christian charity supported allegations of sadistic practices by John Smyth, a prominent lawyer and evangelical leader who ran the camps.

The results of that investigation were never made public, and the allegations were dismissed when they were first reported to the British police in 2013 because Mr. Smyth had moved to Africa and was no longer in the country's jurisdiction. It was not until Channel 4 news disclosed the accusations in a report earlier this year that a criminal investigation was started.

The 1982 inquiry, by Mark Ruston, a close friend of the future archbishop who has since died, was conducted on behalf of the Iwerne Trust, the Christian charity that oversaw the camps. The trust, which was chaired by Mr. Smyth, was a part of a network of camps inspired by the Anglican clergyman E. J. H. Nash, who recruited boys from Britain's elite schools in the hope of evangelizing them.

The report accused Mr. Smyth of subjecting at least 22 teenage boys to savage beatings in his garden shed, with the intent of purging them of perceived sins such as masturbation and pride.

Mr. Smyth, 75, who is keeping a low profile in South Africa, told Channel 4 news that the claims were "nonsense" and declined to comment further.

Although Mr. Ruston concluded that a criminal act had been committed, the trust decided not to refer Mr. Smyth to the authorities. Instead, he was banished first to Zimbabwe in 1982 and ultimately made his way to South Africa, where he faced new accusations in both countries about mistreated boys.

The report was filed away, and members of the trust, including Mr. Ruston, went on to assume influential positions within the Church of England and vowed, one trust insider said, never to speak about the matter publicly.

For decades, the victims suffered in silence, too ashamed to go public with their stories. All the while, they say, the main concern of officials was to protect the reputation of the trust rather than helping them.

"If this came out earlier, Iwerne would have been finished and its members wouldn't have been able to rise up the ranks of the church in the way that they have," said one of the victims, Andy Morse, who added that he attempted suicide twice because of the trauma he said was inflicted by Mr. Smyth.

John Smyth, 75, a lawyer and evangelical leader who has been accused of severely beating boys in a garden shed at one of the elite Christian camps he ran decades ago.

Archbishop Welby, the principal religious leader in the Church of England, says it was not until one of the victims reached out to the church in 2013 that he learned of the accusations against Mr. Smyth. He said he was working in Paris between 1978 and 1982, when the alleged abuse was taking place, and had not kept in touch with his colleagues at Iwerne.

Although no one has produced proof that Archbishop Welby knew about the beatings at the time they were occurring, his account has been contested by several victims and former Iwerne members.

As an officer of the trust, they say, Mr. Welby was close to other senior members of the group and almost certainly would have been briefed on Mr. Smyth's absence and the reason behind it when he came back to visit Iwerne after he graduated from Cambridge University.

While Archbishop Welby claims to have fallen out of touch with Iwerne members during his years abroad, an Iwerne event program shows that he came back to give a talk at the trust's library in 1979.

Moreover, the archbishop and the investigator, Mr. Ruston, were extremely close, as friends and colleagues, the victims and some church figures say, adding that it strains credulity to think that they would not have discussed the matter.

Mr. Ruston was the vicar of the Round Church in Cambridge, England, from the 1960s to the early 1980s, and the archbishop lodged there during his final year at the university in 1978.

Reflecting on their relationship in a magazine article in 2013, Archbishop Welby wrote that, "Mark was someone whose personal holiness shone out in every aspect of his life. We prayed together regularly, talked together a great deal, and I was continually inspired by him to seek to follow Christ more closely."

A Church of England spokeswoman confirmed that Mr. Welby had paid for lodgings at Mr. Ruston's rectory during his time as a student at Cambridge University, but denied that they had been close friends or that they had remained in contact after he left for Paris in 1978.

"He was certainly not aware of any report or the allegations surrounding it," the spokeswoman said.

Yet a senior Church of England figure who has questioned the archbishop's account said that many people had heard about the accusations against Mr. Smyth at the time, but they knew to keep it "hushed up." He withheld his identity because he was not permitted to comment on the issue while the police investigation was ongoing.

"It was a different time then," he said. "Only recently has the church realized how crippling that silence was for the victims involved."

The Iwerne insider, who was friends with Mr. Ruston during those years, said that all the senior members of the trust, including officers like Archbishop Welby, had been made aware of the allegations against Mr. Smyth, even those who had been abroad.

Another church figure, Alan Wilson, a Church of England bishop who is friends with former Iwerne members, said that he found it hard to believe the archbishop's denials.

Andy Morse, one of the victims of Mr. Smyth's alleged abuses, said in an interview that he attempted suicide twice because of the trauma. Credit Andrew Testa for The New York Times

"I have no evidence, but I haven't met a single Iwerne person who thinks it's credible that Justin Welby didn't know that Smyth had left the country under a cloud connected to his behavior toward boys who had been on Iwerne camps," he said.

"Smyth was the chair of the trust, and just the fact that he suddenly dropped his law career and went to Africa would have raised questions," he added.

The matter lay dormant until 2012, when Graham, one of the victims who withheld his last name to protect his privacy, came forward, demanding that the church provide him counseling.

"This whole affair has, I believe, cast a deep shadow over many aspects of my life, affecting my ability to do many things," he wrote in an email to a member of the Church of England. "I have not worked now for 20 years. I want you, within the church, your circle, your elders, to find someone."

In addition to counseling, he said, he was looking for justice, acknowledgment and assurance that Mr. Smyth was not committing the same abuses in South Africa that he is accused of in Britain.

It took six months before he received a response, which said there "might be someone who could help." It was another 10 months before he received another email saying that the person they had in mind was "too busy."

Graham said it was only after he accused Archbishop Welby of knowing about the abuse and threatened to go to the news media with his claims that he was assigned a therapist.

In response to his concerns over Mr. Smyth's activities in Cape Town, Graham was told that the Bishop of Ely in Britain had written to the relevant bishop in South Africa but had not received a reply.

"I know this will be of no comfort to you and I'm sorry I have nothing more positive to say," he was told. "I am hopeful that you may at last find a way to move on from that dreadful experience, in time."

Many of the victims have asked why the archbishop did not reach out to them immediately after he says he learned of the abuse.

"The silence has been deafening," Mr. Morse said.

While the victims acknowledge that the church has made progress in its understanding of abuse in recent years, they have labeled Archbishop Welby an "observer," a term that denotes a person who knew about the abuse but did not report it appropriately.

After more than seven months of silence, Mr. Morse received a phone call from Mr. Welby's office last month asking what could be done for him and other Smyth victims.

Mr. Morse requested that the archbishop give a public interview on the matter and allow the victims to present him with evidence that shows the Titus Trust, which took over from the Iwerne Trust in 1997, lied to the police when the allegations were reported in 2013.

"Leave it with me," the officer said. "I will make sure it happens."

He is still waiting.