The five categories of papal knighthood are, in descending rank, the Supreme Order of Christ, the Order of the Golden Spur, the Order of Pius IX, the Order of St Gregory the Great, and the Order of St Sylvester Pope and Martyr.

The first is conferred directly by the Holy Father but extremely rarely (its last member died in 1993) and is reserved for Catholic heads of state for key involvement in an event attended by the Pope.

Nor are there any living members of the Order of the Golden Spur, an honour made by the pope by motu proprio (Latin for “on his own impulse”). The last member, Jean, the Grand Duke of Luxembourg, died in April.

The remaining three orders are open to Catholics and non-Catholics alike, and to men (knights) and women (dames), with the Order of Pius IX – the Pian Order – the highest award made at present, usually to diplomats.

The Order of St Gregory is for conspicuous lay service to the Church on the recommendation of a diocesan bishop with the support of the papal nuncio. Likewise the Order of St Sylvester is awarded on the advice of a bishop to laity distinguished by their service, particularly in the apostolates.