This summer sees the fiftieth anniversary of the papal encyclical Humanae Vitae, which restated the Catholic Church’s official teaching that the use of artificial contraception in any form was gravely sinful. It caused a furore throughout the Church, particularly when priests who objected to it were disciplined by their bishops. In many cases they were only allowed to resume their duties if they agreed to keep silent.

It was a solution, of a sort, to what was described by the then Archbishop of Westminster, Cardinal John Heenan, as the greatest shock to hit the Catholic Church since the Reformation.