In his Advent Letter to the Church’s primates, Dr Williams steers the narrow path between offering authoritative leadership while trying not to be combative. Liberals and conservatives at either end of the Anglican Communion will be disappointed that he has not drawn the clear lines that they are longing for him to set down in the shifting sands of Anglican identity.

“Better than I feared and less than I hoped for,” was one typical comment on the conservative US website StandFirm.

Liberal websites were more critical. “If the Anglican church cannot accept full equality, then their claims to support human rights for gay people are meaningless and hollow,” said one contributor to the British Thinking Anglicans weblog.

In fact, the letter is one of Dr Williams’ cleverest, most authoritative and most compassionate documents of his primacy to date. He extols both the necessity of Anglican adherence to scripture, and the abhorrence that all should feel for homophobia. But his letter is fundamentally gentle. He is trying to put markers down about the way forward.

The most important of these is more of a question. He is asking how long a Church can sustain people in a representative role within it who are clearly following a path or agenda that is at odds with the majority in the centre ground.

He is pinning his hopes for unity on the Lambeth Conference, at the University of Kent in July next year. By getting as many as possible around the table to talk, and by acknowledging the concessions the US church has made, Dr Williams hopes he can avert schism.

He accepts that it may be too late to stop some on either side from spinning off the edges of the Church. But he believes that there remains core Anglican doctrines, an identity, a communion and an authority around which most can rally.

The key document is the draft Anglican Covenant, a statement of doctrine and belief around which it is hoped the majority of Anglicans will be able to unite. Already, the first draft, known as the “alpha” version is being debated. Soon, the “beta” version, taking into account first comments will be published for discussion at the Lambeth Conference. This will lead to a “gamma” version, the final draft to be sent to provinces for authorisation.

But Dr Williams’s Advent Letter is in fact as good as the covenant. It is the clearest statement of Anglican identity to emerge from the chaos to date. Dr Williams deserves that it succeed in bringing some desperately needed order to his suffering Church.