One fact that hasn’t so far emerged from the first ever state visit by a Pope to Britain is that it follows two state visits to the Vatican by the Queen.
In 1961 she made her first official visit to the Vatican to meet John XXIII. In 1980 she made another state visit to meet John Paul II.
Not every visit the Queen makes is a state one: in the Jubilee Year she met John Paul II as a courtesy after travelling to Rome to meet President Carlo Ciampi on a state visit to Italy.
But as diplomacy is all about reciprocity, it was only natural that the Pope would be invited to make a state visit to Britain.
The question which perhaps really should be asked, therefore, is: why has it taken so long?