An interesting one.
Do as Themas suggests and try and get a picture from the Land Registry as to what land is registered to who.
I did some research and as far as I would work out, a landowner can dedicate a piece of land as a highway (if he chooses to) or an Authority can enable a piece of land to become highway - but only after 40 years use by the public. Or it can happen as a result of a compulsory purchase order, as Themas says. The relevant piece of legislation seems to be the Rights of Way Act 1932.
http://www.glass-uk.org/index.php?option=com_c ontent&task=view&id=236&Itemid=455
It seems the local authority clearly thought it was highway or I do not believe they would have gone around putting yellow lines in place. They have no right to do that on private land.
Check out what the LR says and report back. There are probably other lines of research that could be done for you.