A spokesperson said: "The travellers on Five Acres forced entry to the site by moving large boulders and posts that were put in place to deter this type of unauthorised access.
"There are currently eight caravans, eight towing vehicles and an assortment of trade related vans and pick-up trucks on Five Acres.
"We have also put two large refuse bins on the site."
Sussex Police has been approached for comment.
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