This article appeared in the latest issue of CAM published by the University of Cambridge. I get the mag because I went to the uni back in the late 1980s where I studied Archaeology and Anthropology at Fitzwilliam College.
Anyhow, the piece struck a cord and made me wonder of other transient signs that may be about the place. Keep a look out and please send in any examples.
[posted without permission of CAM/61]