PTS? Please explain!
PTS stands for Personal Track Safety. It's basically a certificate required before anybody can work within the boundary of Network Rail (ie at the side of the track).
More heritage lines now are requiring you take a course in PTS and get the certificate before you can work on the line or be a lineside photographer. Though they're only valid on the heritage line you applied for as far as I know. Even if the guy had one for a heritage line, he still wouldn't of been allowed on Network Rail property.
http://en.wikipedia.org/wiki/Personal_Track_Safety gives a more detailed view.
Hope this helps