The railway exists to give all its patrons a fun day out. When people with tripods and massive lenses ruins it for the family who just want to take a quick smartphone family picture in front of the old train, then we have a problem. There have been multiple instance where the tripod guy has prevented a child a quick picture because they see their picture as more important.

Leave aside the safety issues. When people set up tripods so that they can get their picture, whilst denying others the same opportunity - it's not cool.