In response to students feedback the University of York has changed it's policy on leaving unattended items in the Library.
If items are left unattended for over one hour they will be removed and stored at the Help Desk. This is to prevent students "reserving seats" and preventing others from using study spaces.
All the information about the policy can be found on the library website http://www.york.ac.uk/library/news/unattendeditems/