The Archbishop was appointed largely because of his liberal credentials but disappointed the liberal wing of the Church by siding with conservatives over the issue of gay priests.
Sources close to Dr Williams said that the final straw was the prospect of defeat over the Anglican Communion Covenant, which was drawn up to find common ground around which the various provinces could unite after the ordination of an openly gay bishop, Gene Robinson, by the US episcopal church.
So far about half of the 43 dioceses in the Church of England have voted on the covenant, with 17 voting against and only ten in favour. It appears likely to be rejected.
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Update: From the Times’ Religion correspondent Ruth Gledhill on Twitter–“If you want to bet on an outsider with long odds and good chance of being next Archbishop of Canterbury, back John Inge at Worcester.”