THE ARCHBISHOP OF CANTERBURY is sitting in a chair in the State Room of Lambeth Palace, his face rigid with tension. He hates posing for photographs, so I try engaging him in conversation while our photographer snatches a few shots. For a moment or two Rowan Williams’s face becomes lively and expressive, but as soon as he stops talking it sets again in a concrete grimace, bracing itself against the intrusion of the lens.

The Archbishop rarely gives newspaper interviews; this is only his third since he was appointed nearly two years ago. Like his predecessor but three, Michael Ramsey, to whom he is often compared, Williams is painfully shy of the public eye. Ramsey’s portrait and bust grace the Lambeth Palace corridors: in both, his head is lowered, his eyes downcast so that they can barely be discerned under his bushy brows. Williams too is finding it difficult to cope with the light shining fully and searchingly on his face.

“The sheer level of attention is one of the things I hadn’t quite expected and perhaps that was silly of me,” he admits. “I was thinking about this, actually, before you came. When you are talking to someone who’s hard of hearing, you have to pitch your voice in a certain way and keep it at that pitch. And as you can imagine, I sometimes find this very difficult. It’s one of the things my mother used to shout at me about in her last years.” His voice is indeed so soft that my tape recorder can only just pick it up.

“And as you pitch your voice like that, and try to keep it audible, you become more self-conscious about what you’re saying and perhaps more stumbling, more hesitant. And that struck me as one of the best analogies for trying to speak in a position like this.

“Everybody’s listening — not everybody, goodness, I delude myself! — but a lot of people are listening quite hard for nuances. But of course when you’re speaking in the public register and nuance is difficult to get, you get self-conscious. And I’m still struggling with that."

Williams speaks gently and intelligently, but often obscurely. His prose can be as difficult to unpick as other people’s poetry. Like his Lambeth Palace desk, which is strewn with near-toppling towers of paper, the Archbishop’s brain is crammed with facts, thoughts and ideas.

He has a photographic memory, and can recall whole pages of Russian literature or early theology. Russia is a passion for him: his mantelpiece is covered with icons, and he enjoys showing me a photo of himself with a group of Russian Orthodox patriarchs. “The battle of the beards,” he jokes. “And they have much better hats.”

Not all his audiences, however, are as clever or well-versed as he. Williams has been criticised for using unnecessarily arcane language. But I thought perhaps he had been trying harder in the past few weeks. After all, his sermon celebrating the tenth anniversary of the ordination of women was a model of clarity. “I just wondered . . . ” I begin.

“Why I can’t write like that all the time?” He finishes the question for me and laughs. “It’s not that I’ve been trying in the past few weeks. I’ve been trying for the past 20 years or so and it doesn’t seem to get any easier. I really have to struggle on some levels to say just what I want to say, and yes, I know, I know, I know it’s very clotted. And when it is, it’s partly having to try to formulate something quickly and partly that sometimes the subject matter isn’t wrestled to the ground very easily.”

There seems to be a lot of “struggling” and “wrestling” in Williams’s life — which must be hard for a man who is by nature mild and sensitive. Until he became Archbishop of Canterbury he had never encountered the sheer levels of vitriol that mark the warring sides of the Anglican Communion. He is also battling against an enormous weight of public expectation. Williams says he used to warn his clergy in Wales about dealing with people’s expectation and projection, which intensifies the more senior you become in the Church. He called it “the danger of living other people's dreams”.

Their disappointment, too, must be difficult to handle. "I think that comes with the territory. And again, even when I was Archbishop of Wales and working with new bishops, I used to say, not realising quite how true it was, ‘One of the things you will do as a bishop is disappoint people’."

Williams concedes that people might be disappointed with how slowly things have changed since he became head of the Church of England. “There’s bound to be an expectation that new archbishops make a difference rapidly. But because you’re not the elected leader of a new government with a manifesto to implement and a structure designed to do that for you, the rate of change is bound to be slow. And I’ve said from the start that my job isn’t to be a kind of government leader, to impose a line.

“It can be a slow process, it can be a frustrating process but I think that’s partly the way Christian leadership anyway is set up and very much the way in which Anglicans have tended to do the job.” He laughs: the Anglican Communion, unlike the Roman Catholic Church, has always been notoriously difficult to lead.