London: The new archbishop of Canterbury, Justin Welby, has highlighted the challenge faced by the Anglican church over gay relationships ahead of his enthronement on Thursday, saying he has friends who are in long-term gay relationships of “stunning” success.

The 105th archbishop of Canterbury and leader of the worldwide Anglican community, who will become the first holder of the office to be enthroned by a woman at the afternoon ceremony, has written to Peter Tatchell offering to discuss his attitude to gay marriage after the veteran campaigner criticised it in an open letter.

In a pre-enthronement interview with the BBC, Welby said that while he did not have doubts about the church’s policy in opposing same-sex marriages he remained “challenged as to how we respond to it”.

“You see gay relationships that are just stunning in the quality of the relationship,” the 57-year-old said, adding that he had “particular friends where I recognise that and am deeply challenged by it”.

“The Church of England holds very firmly, and continues to hold to the view, that marriage is a lifelong union of one man to one woman. At the same time, at the heart of our understanding of what it is to be human, is the essential dignity of the human being. And so we have to be very clear about homophobia.”

Questioned as to whether the church could simply ignore some gay relationships, he replied: “It’s not a blind eye it’s about loving people as they are and where they are. You’ll find that in every church and you’ll find that because it imitates the character and the practice of Jesus himself.”

Separately, the Times reported that Welby had emailed Tatchell after the campaigner released an open letter ahead of the enthronement questioning Welby’s rejection of gay marriage.

The letter said: “You claim that you are not homophobic but a person who opposes legal equality for LGBT people is homophobic — in the same way that a person who opposes equal rights for black people is racist.”

Welby reportedly emailed Tatchell to thank him for the “very thoughtful” letter and ask whether the pair could discuss the issue “without the mediation of the press”.

Tatchell said he was pleased by the reply, saying no previous archbishop, “not even Rowan Williams”, had made such overtures.

Welby, an Eton-educated former oil industry executive who joined the church as a vicar in Warwickshire, will be enthroned at Canterbury Cathedral in front of 2,000 guests, including Prince Charles and the prime minister, David Cameron. Among the crowd will be representatives of other major religions.

He will be led to the diocesan throne and installed as bishop of Canterbury by the venerable Sheila Watson, the archdeacon of Canterbury. He will then be led by the dean of Canterbury, the very Reverend Robert Willis, on to the marble chair of St Augustine, marking his appointment as head of the Church of England.