"a closed airfield is like a closed retail store, garage, theatre. It means that it is not accessible without specific negotiation with the owner."
NO. A "closed airfield" in the uk means whatever the operator wants it to. It is common for an airfield to be closed - no fuel, no food, no maintenance, no office to pay landing fee, but you can fly with prior permission. All a pilot has to do is check what the operator had in mind by using the word closed, not a big issue.
Rod1
astonishing as it may seem to those with English as a second language, Rod1 and I are saying much the same thing. If the airfield, store, garage etc. is stated to be closed and you are able to contact the owner or someone in authority over the premises, you may be able to persuade them to let you in, otherwise you don't go