I
wonder how many of those were accessing the site from public computers
in libraries, and what the librarians thought about Wikipedia when
library users notified them of the porn on the Elizabeth II page.
Get the IP (I gather it's an IP user who vandalised the template), reverse WHOIS it, report the issue to ISP / library / school / wherever that IP user belongs.
Last year I had fun kicking up some fuss when an IP editor from Oxford University vandalised an article about my Cambridge college ;)