The last post in this list, Post 217 has not been found but is described as being on the bank of the Thames. This post is about 9 miles from the point opposite Post 217 on the North bank and about 5 miles from the nearest point on the bank. Why the vast gap? Have all the posts disappeared?
Some possibly have disappeared but I think the answer is also that this area was very marshy and there were few roads through it.

On Barking & Dagenham / Havering boundary. Note seam in road surface.

See this page on the Hainault Forest website

++++ bring in write up from wip_nor and link to link

Post 6 should be in the hedge just to the left of the sign but I could see no trace of it. Note seam in road surface.

Hog Hill Road. Apparently, lurking in the vegetation near the speed limit sign there is the Collier Row stone, one of the Hainault Forest boundary stones. The write-up says a "lamp post … was digitally removed". I presume by "lamp post" they actually mean the speed limit sign.