Many people arrived early 'in the mistaken/erroneous belief that' [=because they mistakenly believed that] free tickets would be available.
It's my 'belief that' the current policy is certain to fail. [=I believe that the current policy is certain to fail]
There is a 'growing belief that' [=an increasing number of people believe that] these policies will not succeed.
(..) Where were they headed? They killed King Aelle near York and they're moving south into the midlands, so far, towards Repton. Is it your belief that they are set upon attacking my father's kingdom? That they have gathered together to attack Wessex? There is no doubt in my mind. (..)2017 TvShow: Vikings Title: On the Eve Season: 4 Episode 19