Ten years ago Benedict XVI released one of the most momentous texts of his pontificate. Summorum Pontificum lifted restrictions on the so-called Tridentine Mass. The motu proprio decreed that there are two legitimate forms of the Roman Rite: the Ordinary Form (post-Vatican II) and the Extraordinary Form (pre-Vatican II). The two forms should be “mutually enriching”, rather than antagonistic. This was the German pope’s blueprint for ending the “liturgy wars”: the bad-tempered debates that have consumed so much energy since the 1960s.