According to wikipedia this method of cooking has been used all around the world - which makes sense. There are different variations which can be used even for smoking or steaming food. In our experiment we wanted to try a "robbers' version" - a quick make-shift pit with no intention of building a reusable structure. In Finland some people have permanent ground ovens; floor and walls made of bricks, and a metal lid for sealing. That kind of structures are often smaller, suitable for cooking 2 or 3 kg of food in one go. I've also heard people using natural cracks in a cliff instead of a pit dug in soil.

(Hmmm, if I was a land-owner in UK, I'd set up a "primitive camping area" - a private property, where people could enter for a very small fee, and then they would be allowed to use a modest amount of natural resources, start fires, fish and forage according to their skills...)