Which still doesn't answer the question of WHY you would be stopped and asked to produce a ticket and credit card anywhere other than on entry to the ground or inside the ground?
Criminal Justice and Public Order Act 1994
"If a police officer of or above the rank of inspector reasonably believes—
(a)that incidents involving serious violence may take place in any locality in his police area, and that it is expedient to give an authorisation under this section to prevent...
I'm sure Edna will happily correct you on this but any stop made under that act will need prior authorisation, need to be conducted by more than one officer and need to be logged and written up after. They won't be going around stopping and searching people (and they'd have to perform a proper...