I know what you mean: to my mind the neolithic crowd were (ie are) essentially modernists, the new kids on the block.

Bits I am pulling together suggest there have been roman finds at the Enfield "fort" but both English Heritage and the National Monuments Record folk seem pretty clear it is iron age. So maybe yet again it is a case of colonial takeover of already occupied sites. In addition my guess would be that coming years will find increasing numbers of "iron age" centres turn out to have rather longer (pre-)histories than we currently tend to assume.

Certainly it is a fine thing to find such a place on the proverbial doorstep.

By the way I ive in Edmonton, where I notice there are not so many trees.

Treeman