The Incarnation unites us all round the crib at Bethlehem. But what kind of unity is there among Christians today? Here, the Archbishop of Canterbury looks ahead to January’s centenary Week of Christian Unity. It raises uncomfortable questions, he says, not least about communion.

A hundred years on from the establishing of the Week of Prayer for Christian Unity, how much further forward are we? And what exactly are we praying for during this week of prayer? On the whole, it’s become a fixture for most “mainstream” denominations, a few days when the more enthusiastic or more biddable members of the congregation turn up to someone else’s church for a well-mannered but often rather lukewarm joint service or two, or perhaps for a talk by a prominent local leader.