We discovered several years after erecting our polytunnel that it may have required planning permission but to date, nobody official has queried it. It sounds as if you might have one or more picky neighbours if someone reported you for keeping livestock on a holding
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If it were me, I'd phone up the planning department and get advice directly from them. If they have told you it's ok to erect one nobody can call you out on it. Ask for it in writing though, cover your back. Good luck.
Pretty much what CC said I just realised
She has legal expertise of course, very handy sometimes.