There is really no problem with anyone hanging a flag on their own property or elsewhere with the owner or responsible person giving permission.  What we seem to see is people hanging flags everywhere, in places where they are dangerous or the act of hanging them could be dangerous, such as over road carriageways in the hope someone will tell them to take it down so they can raise a bit of chaos

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Wonder if you could email a request to the club and arrange to leave the chosen item at the ground and the team or individuals could sign it ready for you to collect later that day.