My favourite “Dean” tag was way out of town. I used to get the train from St. Albans to Brighton every other weekend for a good while (before I lived here), and between Three Bridges and Haywards Heath, it went over an old bridge overlooking some fields. In one of these fields, in the middle of the countryside, was a “Dean” tagged on the side of a water trough.
I’ve not seen it for ages, but hopefully it’s still there. The other thing I used to see was the big field of red telephone boxes near Crawley. Sadly they’re not there any more.