At the heart of Antonia Fraser’s utterly gripping and consistently witty history of the struggle for British Catholic emancipation lies a paradox. The 1829 act of Parliament that allowed Catholics to take their seats at Westminster – to the disgust of George IV, the king of the book’s title – might never have passed had it not been for the horrifying anti-Catholic persecution that preceded it. Priests loyal to Rome were hunted down and murdered with Stalinist zeal, sometimes by the government, sometimes by anti-Catholic mobs. Nuns were executed like cattle in an abattoir. And all this in a supposed bastion of civilised liberty.

That was in France, of course. No other western European nation has butchered as many Catholic clerics. The persecution across the Channel horrified the English public, which suddenly remembered that Roman Catholics were Christians too. Anti-popery was not wiped out by the French Revolution, but it learned some manners.

The King and the Catholics nicely illustrates the shift in attitudes with a scene on Shoreham beach in Sussex in 1792. As a ship carrying expelled nuns from the Loire approached the shore, en route to Belgium, the captain warned the sisters that a crowd was waiting. This was