Prince Charles' sensibilities are clearly similar to those of his mother who, as heir to the throne, set out the enduring themes for her life in 1947. As Princess Elizabeth she was on a tour of South Africa with her family when, on her twenty-first birthday, she made a speech broadcast by radio dedicating her life to the service of the Commonwealth.

The future Queen stated, in the confidence of "an unwavering faith, a high courage and a quiet heart", that "my whole life whether it be long or short shall be devoted to your service". This mandate was solemnly sealed at her later coronation, during which, at its most sacred moment, Elizabeth became quite literally set apart and anointed by God (so sacred was this rite that it was not shown by television cameras or recorded on film).

This firmly Christian commitment has provided the bedrock for the Queen's entire reign with, at its heart, what one senior prelate commended as an "uncomplicated faith".

Her eldest son's own faith is perhaps less clear-cut and more embellished, yet it too has been a driving force throughout his life. At the age of 20, he entered into solemn commitments "in faith and truth" at his investiture as Prince of Wales. Ever since, he has pursued a spiritual quest of great breadth and depth causing some proponents to speculate, naively, that he was on the point of conversion, all at once, to Russian and Greek Orthodoxy as well as Islam. The truth is rather that, as he once explained to Jonathan Dimbleby, "I am one of those people who searches. All the great prophets, all the great thinkers, those who achieved a far greater awareness of the aspects of life which lie beneath the surface, all share the same understanding of the universe, of the nature of God, of the purpose of our existence, and that's why I feel it's so important to understand the common threads which link us all in one great important tapestry."

The practical reality is, however, that he is a personally sincere Anglican Christian. He has his own chapel at Highgrove -- his house and estate in Gloucestershire -- and close friendships with a number of bishops including the Bishop of London, Richard Chartres, and the retired Bishop of Liverpool, James Jones, as well as the former Archbishop of Canterbury, Lord Carey, who has spoken warmly of the Prince as "a man of great stature and vision" and "a committed Anglican who takes faith seriously".

Nevertheless, in the quest to reach out to everyone in the realm, Prince Charles has been tempted to interpret the historic title of English monarchs since Henry VIII, of Fidei Defensor, to mean defender of faith in a wider sense, rather than merely Christian. This prompted the recently retired Archbishop of Canterbury, Rowan Williams, to issue an unusually blunt clarification stating that as Defender of the Faith, the monarch "has a relationship with the Christian Church of a kind which he [or she] does not have with other faith communities". Against this background it is striking and telling how publicly Prince Charles has taken up the plight of Christians in the Middle East. At a reception for them last December at Clarence House, he said the decline of Christians in the region represented a major blow to peace as Christians are part of the fabric of society. "For 20 years, I have tried to build bridges between Islam and Christianity and to dispel ignorance and misunderstanding ... [but] we have now reached a crisis where the bridges are rapidly being deliberately destroyed ... through intimidation, false accusation and organised persecution," said the prince.

On Wednesday last week, Prince Charles spoke out on behalf of Armenian Christians facing persecution in Syria and Iraq. They are descendants of survivors of the Armenian genocide committed by the Ottoman Government. They fled to Syria a century ago.

Addressing the Primate of the Armenian Church in the United Kingdom, Bishop Vahan Hovhanessian, at the church of St Yeghichè in London, he said: "I greatly admire the courage and faith of your flock who are an example to us all of faith, quite literally, under such grotesque and barbarous assault."

As heir to the throne, which is by convention above politics, there are certain restraints upon what Prince Charles can say and how forcefully he can say it. Yet he has dared to speak out directly when others -- most notably Western political leaders -- have shown a reticence and hesitation that is hard to explain.

On 4 November, in his video message for the parliamentary launch of the "Religious Freedom in the World Report -- 2014", compiled for the charity Aid to the Church in Need (ACN), he told religious leaders that they have a responsibility to ensure that people within their own faith tradition respect those outside it, saying: "We have yet to see the full potential of faith communities working together." He also called for an acknowledgement that the future of a free society depends on recognising the crucial role played by people of faith.

To speak in this way is to take on two major issues at once. First, it is a challenge for the Middle East to preserve the place of Christians and other minorities within it. Here, once again, it is important to note another royal thread. For in making this point, Prince Charles enjoys the support of several royal families in the region and most particularly that of the Hashemite Kingdom of Jordan. He has worked extensively with both Prince Hassan and Prince Ghazi of Jordan and is close to King Abdullah, who has led the nation in offering a refuge to displaced Christians from Iraq and Syria despite having far too few resources for the task.

One of the most striking features is the royal solidarity across the region -- from Saudi Arabia to Morocco -- with the British royal family by virtue of history and standing. Also notable is the fact that amid the upheavals of the "Arab Spring" the region's monarchies have so far proved significantly more stable than many of the republics.

But Prince Charles has also challenged the West, where the public doctrine of the state is seemingly ever more secular. In the face of this, to link a free society to the role of faith is an act of courage indeed.

Inevitably, there are those who have been keen to allege that Prince Charles is somehow improperly meddling by expressing any views in public at all, and even worse in expressing his views to members of the Government privately. This has led to long-running attempts, led by The Guardian newspaper, to force public disclosure of his letters to Ministers. In his defence, the Prince's Private Secretary, Sir Michael Peat, has distinguished between "political issues" and "matters of public policy" and indicated that "if an issue becomes party political or politically contentious after His Royal Highness has raised it ... he will not do so in public again". Within this framework, the matter of Christians in the Middle East engages Charles on the religious and humanitarian level, which is a cross-party matter. And he is also well covered by the public interest dimension, while the more he engages, the more he creates precedent for expanding the liberties and role granted to him through emergent convention and "accepted practice".

The definition offered by the former Lord Chief Justice of England, the late Baron Widgery, that "a true convention is one founded in conscience" would seem most fitted to the prince's case. For that, in the end, is the ultimate grounding of his concerns, informed as his conscience is by the fullness of his royal vocation.

In 1947, as the Queen came to the end of her dedication speech, she referred to a motto -- which belongs to successive Princes of Wales -- "Ich dien" ("I serve"). Perhaps this German phrase can itself be illumined by a Latin one, highly appropriate to Prince Charles: "Servire regnare" ("To serve is [truly] to rule").

The Revd Canon Alistair Macdonald-Radcliff served as senior adviser to the World Economic Forum's Council of 100 and was Quondam Dean of All Saints' Anglican Cathedral in Cairo