Over the past five years, migrants and refugees have flowed into Europe in unprecedented numbers, arousing deep concerns about their impact on host countries. What is not clear, though, is how much impact the new arrivals will have on Europe’s religious alignments.

The main effect will be to swell the Muslim population. But alongside the Muslim influx are Christians of various kinds. Their actual numbers are open to much de­bate. A limited number of the new arrivals come from ancient churches in Syria and Iraq, but far more common are the African Christians who are not fleeing any particular conflict, but who are migrating in search of a better life.

Their presence has found an evocative material symbol in the makeshift tent church erected in the camp at Calais, in France, among the many thousands of desperate mi­grants struggling to reach Britain. Many of the church’s attenders are Ethiopians and Eritreans, from Christian communities that were already well established when France itself was still pagan soil.