It really is a Serious hobby for some. Pulled a Stobarts trailer once, stopped in services and was confronted by E S spotters, they were shocked that i did not work for Stobarts but told me about the registrations and cab names that had pulled that trailer. They were tipped off that one of the drivers who was on the Stobart tv programe would also be stopping at these services, that who they were waiting for.
These people have photo albums of all the trucks and trailers owned by Stobarts. They even told me how they get the names of the units. Only 2 have male names, Valentino in memory of Valentino Rossi and Lee Rigby.
Only reason I knew, there was an ES fly on the wall series on (C5 about 6 years ago?) where they featured those people. I like these very British obsessions.