http://www.pastscape.org/hob.asp?hob_no=405526&source=textonly&period1=Iron%20Age&county1=Greater%20London&class1=None&hob_name1=Hillfort&min_date1=ALL&max_date1=ALL&type1=&place1=enfield&page=first&recs_per_page=5&s_o=1
Also Enfield Archaelogical society should have some information....
Thank you for the link, which basically confirms what the MNR people have to say.
Treeman