Snow swirls around the palace and the Archbishop of Canterbury turns to the fire blazing in his inglenook: “It’s been a turbulent six months.” The next six will see a far greater storm and this most turbulent priest will be in the eye of it.

He warns King Tone against setting himself up as a “moral policeman” around the world and declares that war against Iraq now would be “unacceptable to me as a Christian”.

The Prince of Wales might also send murderous knights galloping down the M2 to Canterbury as the archbishop warns the heir to the throne that he must be crowned as a Christian and, unless parliament declares otherwise, rule as one.

Nor is our new archbishop squeamish about upsetting liberal sensibilities, suggesting that we should hold asylum seekers in secure accommodation while they are put through a rigorous vetting process and then swiftly rid ourselves of those who pose a terrorist threat.

Last month Rowan Williams secretly slipped off to a rustic retreat in Italy for silence, cold showers and prayer, but now that he has received his orders from heaven he will make his call to the clap of thunder. The Church of England will no longer slink around apologetically at the back of society like a slightly retarded misfit.

“Christians have got to give the impression that what they take seriously isn’t a million miles from what other serious humans take seriously.” In fact, he says, they come from all walks of life and they are just as concerned with the world beyond their pews as anybody else: “In terms of people who are willing to take responsibility for the society they’re in, the church is quite well represented.”

He is an intellectual with deep convictions: not a charge often levelled at his predecessor George Carey. It is a credit to Blair that he appointed him, because Williams will be trouble.

“Any Christian pastor doing their job will at times be uncomfortable (to government). The great theologian Karl Barth said that. The Christian is always a bad party member,” smiles Williams, who discloses that he is a lapsed Labour member.

“Christians are called to fidelity and integrity. I’m not sure that for pastors it is terribly good to be identified with one particular party. You may lose the freedom to ask questions.”

He is certainly asking questions on Iraq, using “every channel” to push his anti-war agenda, and has counselled Blair “in private, and will continue to do so after the outbreak of hostilities”. It doesn’t require divine powers to discern his message. War will cause a “humanitarian catastrophe” in Iraq and the surrounding region, not least because millions of refugees will have a destabilising effect on neighbouring countries. On the situation in Iraq itself the strength of his feelings is clear.

“Outside the presidential palaces, civil society has unravelled, infant mortality has trebled in 10 years, one child in four is born underweight, one child in five is malnourished. Is the best way of engaging with so fragile and desperate a society military action? I think that has to be a very serious question.” Williams does not merely argue for peace; he wills it.

He deploys arguments political (“There has been some degree of compliance (with the United Nations) and openness as well. It’s a start”) and moral (war is unjustified without tackling the “open sore in the Holy Land”). He talks about his belief in the need for a regional security policy in the Middle East and the deep anxiety that Christian communities there and in Pakistan feel about the backlash they might suffer after an American-led attack on Iraq.

He also assaults Blair’s post- 9/11 agenda, reflecting on “the extraordinary difficulty in the notion of being a moral policeman. You immediately discover that what you say is mired in complex questions that undermine your authority.”