Though I wouldn't be surprised if he's already got it. :)
Medieval Graffiti: The Lost Voices of England's Churches (http://www.amazon.co.uk/Medieval-Graffiti-Voices-Englands-Churches/dp/009196041X)
I've seen the occasional bit of old graffiti here and there in European churches and elsewhere. The Pont du Gard has some, but the earliest date I was able to spot there was 18th century. Here's a link to an article about the book linked above which examines some interesting medieval graffiti in English churches. "Witch Marks, Curses, and Magic in the Neglected History of Medieval Graffiti" | Hyperallergic (http://hyperallergic.com/266861/witch-marks-curses-and-magic-in-the-neglected-history-of-medieval-graffiti/)
Bump, in case this dropped off the "unread posts" list before Old Git returned and had a chance to see it.
Yes, I missed it before. Very interesting stuff, Recusant, thanks!