Visiting the annual Greenbelt Christian festival served as a reminder of both what can unite Christians – and divide them. Could Pope Francis, who is succeeding in bringing them together, step in to sort out a very English problem? I have seen the sun break throughto illuminate a small field for a while, and gone my wayand forgotten it.So wrote the Welsh poet R.S. Thomas. Only later, after he had moved on, did he realise that the field he had glimpsed was the one in which the pearl of great price was buried. His poem, called The Bright Field, was taken as the theme of this year’s Greenbelt, the Christian festival billed as a place in which “arts, faith and justice collide”.   The four days of talk, song, laughter and action were littered with moments tha