My sister has just returned from a college trip to Manchester. They were taking photos for their art course. The theme was transport. A small group of them decided to go to a railway station to take some photos of some trains. They were then approached by a community support officer who told them that they couldn't take photos of any of the trains without prior written permission from the station manager. Not wanting to get into an argument they just went elsewhere. Is there any legal reason for this, or was the CSO just being awkward?