For years my mental map of Europe nicely included religion as a boundary marker: Orthodox Christianity held sway in the east, while the Church of Rome generally had the upper hand in the west. Of course that was too simplistic; it neglected a dozen flavours of Protestant belief, not to mention Judaism, Islam and other faiths. But somewhere around the western boundaries of the former Soviet Union, the alphabet seemed to change into exotic Cyrillic, and at about the same point Catholicism gave way to the onion domes, soulful chant and Slavonic rites of the Orthodox Church.

The real world turns out to be a shade more complicated.