You haven't given a map ref Baz, which would have helped, but looking on Old-maps, start at Streatham. Go left (West), and there's a Wood Lodge marked. Slightly above this is a splodge on the map, which may or may not have read 'Stone' at some point - just below the 'portions' legend on the map.

Could this be it? If so, it was there in 1874 - not quite prehistoric, but at least we know it's not 'modern' in the 1960's regeneration sense!

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