NOT FOR THE first time, I find that an idea I had nursed for a book has actually been written. Beard Theology: A Holy History of Hairy Faces, by the blogger known as the Church Mouse, gives a spirited account of the ways in which men’s beards have been given theological significance. I haven’t read it yet but I gather it includes an account of Peter the Great’s assault on Russian beards after his return from his tour of Western Europe, an orgy of barberism from which only the Orthodox clergy were exempt.

The symbolism of beards loomed large in the West during the Reformation, when Protestant divines grew great spadelike beards to flout the Roman custom. Your religion was on your face.

But what really got me going on the subject wasn’t so much facial hair as the absence of head hair that’s known as a tonsure, which middle-aged men often replicate when they go bald. Bede had strong views on the subject, pitting the correct Roman tonsure against the subversive Celtic one. The former, he declared, replicated the crown of thorns – that’s the one we’re used t