I saidI wasn't going to make a habit of this, and I'm not, but I've ticked off nine more.
This is the northwest corner of London, from South Harefield round to South Oxhey, annotated with all the places you can cross the boundary by car, train or public footpath. Away from Northwood it's surprisingly impermeable.
The black ticks are all the crossings I've crossed and my latest tranche are on the eastern side of the map between Batchworth Heath and Oxhey Woods, i.e. this bit.
What's really unusual about this stretch of the Greater London boundary is that it's defined by a two-mile long footpath threading through suburbia, and a footpath so quiet that I met absolutely nobody else along the way. Let's walk that path.
All the exits from London :Rickmansworth Road, Batchworth Heath
This is the busiest road across the boundary on my map and it's still not ridiculously busy, just the A404 winding its way to Rickmansworth past Mount Vernon Hospital and Moor Park Golf Club. Not only are there signs welcoming you to Three Rivers and Hillingdon there's a also a coal tax post, which is always a fine portent of a borderline space. I've crossed here several times before, and if you've walked London Loop section 13 you've crossed too. The footpath we seek is numbered R1 and bears off into woodland just south of the blacked-out Prince of Wales, where the exotic dancers performing yesterday afternoon were Sabrina, Sara, Nicole, Virginia and Larisa. The boundary path is forget-me-not-fringed and scattered with celandines, but also required me to dodge a decaying fox and a toppled tree so it wasn't all lovely.
All the exits from London +1:Farm Road
Farm Road is less a road and more a shabby track, once driveable, and crosses the boundary a few steps uphill on the way to Batchworth Lane. Here the footpath number increases to R2, indeed it'll be rising incrementally for the next two miles eventually peaking at R8. The next stretch is the nicest part of the walk, opening out into a clearing with bluebells and butterflies, although the line of pylons doesn't help and I fail to understand why someone had scattered 13 tube maps across one small area of undergrowth.
All the exits from London:Kewferry Road, Northwood
This is as far as London Loop 13 follows the boundary, next veering off towards hoity toity Moor Park, so I'd crossed this one before too. Check the bins to either side of the footpath to confirm that one side is in Three Rivers and the other is in Hillingdon. Kewferry Road, incidentally, is where they filmed the exterior shots for The Good Life in the 1970s with Margot & Jerry's house, then Tom & Barbara's, a few doors down on the London side. To follow the boundary proceed onto footpath R3 which runs round the back of St Martin's Junior school. Unusually the school and playing field are in London but their all-weather sports pitch is through a gate fractionally into Hertfordshire, and double unusually their nature area contains a coal tax post.
All the exits from London +1:Sandy Lodge Way
The next suburban avenue to cross the boundary is Sandy Lodge Way, a backroad linking Northwood town centre to the much bigger houses in Moor Park. Ahead we enter footpath R4 which has been made entirely inaccessible to motorcycles by the cunning method of planting a tree in the middle of the path 100 years ago.
All the exits from London:Metropolitan line
I've exited London here by train hundreds of times, but never walked this shady footbridge over the top.
All the exits from London +1:Footpath 53
On the other side of the railway is a quiet crossroads of four footpaths. Only the Hillingdon paths are fingerposted, specifically R4 (west), R5 (east) and R9 (south). To exit London take the unmarked path into the woods - a couple of steps ought to do it - which is footpath 53 to St Mary's Avenue.
All the exits from London +1:Eastbury Road
Another street of Metro-land detached houses divided by a footpath, an unseen boundary and entirely different council tax bills.
All the exits from London +1:Little Stream Close
This is an administrative curiosity, a cul-de-sac less than 100m long which starts in London and switches to Hertfordshire halfway down. The dividing line is again an age-old footpath following a former field boundary (now numbered R6). Fortunately for the binmen all the houses are at the Hertfordshire end.
All the exits from London +1:Eastbury Avenue
The suburban streets are coming thick and fast so I've been racking up the boundary crossings here. But the next stretch of footpath (R7) is a lengthier divide, squeezing between a sequence of back fences in various states of disrepair. Nobody has a back gate onto this godforsaken cut-through but several could sneak out through a tumbledown gap if required. Also this path includes the very closest point in Greater London to Northwood Headquarters, home to NATO Allied Maritime Command, so anyone standing here at the start of WW3 is likely to be the first Londoner to be vaporised.
All the exits from London +1:Mountview
Another administrative curiosity, a cul-de-sac less than 200m long which starts in London and switches to Hertfordshire halfway down with the dividing line again this age-old footpath. Its luxury houses were squeezed into a back field after the war, hence the necessary disregard for boundaries, and this time some residents live on one side and some on the other. Everyone avoids ULEZ, thankfully, but bin day for the first six houses is Monday (weekly) and for the other ten it's Tuesday (fortnightly).
All the exits from London:Watford Road
This is another main-ish road, this time connecting Northwood to South Oxhey, Bushey and Watford. It's the first time since Batchworth that Hertfordshire have bothered to erect a welcome sign, but Hillingdon never seem to miss an opportunity to remind drivers they were once the Large City Winner of Britain in Bloom. What follows is footpath R8, another weaving walk between fence panels and wire netting with occasional glimpses of inaccessible cul-de-sacs. Just as a reminder, I haven't seen a single other person on this path over the last two miles because this boundary is not a desire line.
All the exits from London:Potter Street Hill
The sequential footpath finally ends at the lofty meeting point of three very private roads, one of which leads to Pinner Hill golf course. Only the emergency services can unlock the bollards and drive across the divide. This summit is the highest point in the borough of Hillingdon, 134m above sea level, which means I've been here previously for blogging purposes otherwise you really wouldn't.
All the exits from London +2:Oxhey Woods
I decided to carry on briefly down South View Road because two footpaths bear off into Oxhey Woods (and into Hertfordshire) and I couldn't remember which one I'd done before. Now I've done them both and the bluebells were magnificent. For good measure I also crept back into London via the contractors car park at the golf club while nobody was looking, making a grand total of nine fresh crossings since today's post started.
I think my next uncrossed boundary is at Hive Road in Bushey Heath, three miles further on, then another two miles to Centennial Park. But let me reassure you I am absolutely definitely not trying to tick off every single crossing of the Greater London boundary because there are far too many of them and they're not always well defined, not to mention extraordinarily tedious for you lot.
