Ooh - careful Ethel. I have great respect for your wide knowledge, but on this one, I'm not so sure. I think the issue is that land has to be on the Register of Common Land held by the County Council. Village Greens can also be registered. There are an awful lot of 'commons' that exist that are not registered - they are either not owned by anyone, or they are legally owned by the local council or they are privately owned. The whole situation at Newton Common near Newbury on which landmark legal cases were made came about because the land was privately owned yet under an agreement where the maintenance of the common was done by the council. (this was about access rights across the common - not building on it).