This idea was first expressed to me by Alan Denman of Stinging Bull Films in Los Angeles – I met Alan and his partner Ayesha Walker whilst waiting for my US visa and I now conclude that I went to the embassy specifically to meet them, rather than to get a visa. I found the above schematic which seems to capture the essence of it on the web site of an old friend of mine, Maddy Harland who is responsible for bringing permaculture into many people’s lives.