Hans Zollner is one of those Catholic priests who have more air miles to their name than many business executives. And the files in his briefcase are far more serious than those of a hedge-fund manager or a globetrotting corporate raider. The 51-year-old German Jesuit is one of the Church’s greatest experts on the sexual abuse of children by priests, and one of Pope Francis’ key advisers in the scandal that is again engulfing the Catholic Church and threatening to overwhelm Francis’ papacy.

This week Fr Zollner, the president of the Centre for Child Protection at the Gregorian University and a member of Francis’ Pontifical Commission for the Protection of Minors (PCPM), is flying to the United Kingdom on a rare visit.