After much conjecture we now know how to address Pope Benedict after he retires. This morning the Vatican announced he will be called "emeritus pope," and will continue to wear white. This is one of the more straightforward elements in what's proving to be a complicated transition. And it has made has been complicated further by the resignation this week of the United Kingdom's most senior Catholic – Cardinal Keith O'Brien – for alleged inappropriate sexual behavior towards other priests.   Few people are better placed to shine a light on what might emerge in the coming weeks than David Willey, the BBC's Rome Correspondent.