If you are considering walking this route yourself, please see my disclaimer. You may also like to see these notes about the maps and GPX files.
I turned left along the drive (the OS map shows that it is a byway) and followed it to the buildings at Northchurch Farm. Here I turned right and followed another byway. After a while this turned right, passing a small estate of bungalows on my left. When I reached a path junction, I turned left, still on a byway and still next to the bungalows. Over the hedge on my right I saw some Fallow Deer in a paddock or enclosure, I have often seen them here before. At the end of the byway, I turned right onto a footpath that ran along the left edge of a large ploughed field. I soon passed a pond, and then a tree belt started on my left, which the path followed for several hundred yards.
The drive to Northchurch Farm (a byway)
The byway after I turned right at Northchurch Farm
Further along the byway, as it passes the small estate of bungalows
Fallow Deer, in a paddock after I turned left
The byway after I turned left
The start of the footpath, after I turned left at the end of the byway
Further along the same path, approaching a pond
Pond beside the footpath
Further along the same path
At the end of the tree belt the path turned left (I noticed that a permissive path went right here, linking up with the path I usually take when I'm in this area). I had another ploughed field to my right here. On reaching a field corner I went straight on, with a large paddock to my right (over a wire fence), the formerly level path now starting to descend slightly. The path then turned half-left into a wood, soon reaching the bottom of a small valley and starting to go up the other side. Leaving the wood, the path continued uphill across Alpine Meadow nature reserve (I've only walked this path once or twice before and that was many years ago, I didn't remember this nature reserve at all). Beyond the small nature reserve, the path flattened out again and ran along the left edge of a number of paddocks (one of which had some colourful Show Jumping fences in it).
The same path after it turns left (where a permissive path goes right)
Further along the same path
The same path, where it goes through a wood
The same path crossing Alpine Meadow nature reserve
Looking left at Alpine Meadow nature reserve
The same path continuing from Alpine Meadow nature reserve