While paying tribute to Pope Benedict XVI, as expected, British church leaders are among those signalling questions about the future of the papacy.
Coded references to "challenges" facing the church and global Christianity are common features of the statements emerging from the denominational headquarters today.
The Methodist Church in Britain was among the first to respond to the ailing Pontiff's unexpected resignation this morning (11 February 2013).
The Rev Ken Howcroft, who represents World Methodism in Rome, commented: “It is sad when a Christian leader has to lay aside an office in this way. I was present when the Pope presided at a service to mark the end of this year’s Week of Prayer for Christian Unity."
"His address was excellent and clear," Howcroft continued, "but he has started to look more frail recently, and there are great challenges urgently facing all our Churches. It will be fascinating to be in Rome as a new Pope is found.”
The new Archbishop of Canterbury, Justin Welby, observed: "In his visit to the United Kingdom, Pope Benedict showed us all something of what the vocation of the See of Rome can mean in practice – a witness to the universal scope of the gospel and a messenger of hope at a time when Christian faith is being called into question."
The Archbishop of York, Dr John Sentamu, referred to the Pope as "a true successor of St Peter", the formal Catholic claim, and noted that he had issued a "challenge [to] a culture that is so self-referential."
Archbishop Vincent Nichols, who has tellingly not been made a Cardinal under Benedict's pontificate, released a statement saying: "The Holy Father recognises the challenges facing the Church and that 'strength of mind and body are necessary' for his tasks of governing the Church and proclaiming the Gospel."
"I salute his courage and his decision," said the president of the Catholic Bishops Conference of England and Wales.
UK Prime Minister David Cameron, whose government has pursued a reform of civil marriage law that has attracted huge opposition from Benedict's supporters, made a brief statement, saying: "Pope Benedict has worked tirelessly to strengthen Britain's relations with the Holy See. His visit to Britain in 2010 is remembered with great respect and affection. He will be missed as a spiritual leader to millions."
Scottish Catholic Cardinal Keith O'Brien said: "I know that his decision will have been considered most carefully and that it has come after much prayer and reflection."
England and Wales has no voting-age Cardinal available for the Conclave that will choose a successor to Benedict. When it is called to vote, these islands will be represented by Cardinal Brady (Ireland - north an south) along with Cardinal O'Brien (Scotland).
From the grassroots, many faithful Catholics "are crying out for change, hope, life and energy to sweep through the institution," one insider told Ekklesia today.
"The pope’s decision to step down from the papacy offers the Catholic Church a unique opportunity for reform of the Holy See," theological commentator Josef Gustafsson said on Twitter.
Catholic theologian Professor Nicholas Lash, who was at Vatican II, the great reforming council, told The Tablet, the weekly paper, that Pope Benedict's decision "has put him up in my estimation, as it was a courageous and wise move to take."
Pope Benedict has many critics as well as admirers, some a mixture of both, inside and beyond the institution of the Catholic Church.
He has been a staunch opponent of women's ministry, of change in the work and culture of the hierarchy, of relaxing regulations around priestly celibacy, of changes to the church's position on contraception in the midst of the AIDS pandemic, and of other reforms that those who wish to see change believe are vital for the renewal of the Church.
Above all, he has had to cope with a devastating series of sexual abuse crises, and of continual allegations of cover-ups, which have struck a huge blow to the trust of millions of people in the Catholic Church.
There have also been serious questions about the Vatican's finances and about the general secrecy surrounding its administration and operation.
Voices from the developing world, including those of some priests and religious, say that the Church's unbending position on birth control has had a terrible impact among poor and vulnerable communities.
Under Benedict's reign, progressive voices within the Catholic Church have also been silenced or marginalised, and determined conservatives promoted at every opportunity, critics say.
One strong supporter, Daily Telegraph commentator Damian Thompson, a former editor-in-chief of the Catholic Herald newspaper, while eulogising the pontiff, admitted: "There have been been public relations disasters, notably over the readmission of ultra-traditionalist bishops to the Church, one of whom had Nazi sympathies."
However, the immediate focus of public commentary is likely to be first on acknowledgement of Pope Benedict's gifts - including a rigorous intellect, outspokenness against war and poverty, and sustained work on Jewish-Christian relations - and then on conjecture about the process and outcome of choosing a successor.
"Two Cardinals from Africa were today among the frontrunners to replace Benedict XVI, raising the prospect of the first modern black Pope," declared the Times newspaper, beginning what is sure to be a welter of speculation.
* Benedict XVI leaves a mixed legacy on ecumenical dialogue, by Stephen Brown - http://www.ekklesia.co.uk/node/17981
* World churches chief 'respects decision' of Benedict XVI to resign - http://www.ekklesia.co.uk/node/17975
* Will Cardinal Martini's '200 years out of date' comments echo in the Conclave?, by Simon Barrow - http://www.ekklesia.co.uk/node/17976