When my parents had their extension built, my dad had a small secret box room buit in to the cavity created by the recessed fire place. It was accessed by removing logs from the recessed log store and climbing up and in . Was shelved full height, about 1.5m deep and about 5m long. As a young boy (aged about 25) I thought it was epic and I had visions of him storing weapons, valuable wine, gold bars and porn in there, or creating a panic room.
As it was, I don’t think he could ever be arsed to remove the logs so didn’t really use it for anything other than a small amout of cash he got from doing some business off the books.
But it was there……