Under the flight path: traffic free cycle routes across the M4 corridor at Heathrow Airport

In his psycho-geography column in the Independent, Will Self describes his walk from his home in Central London to New York. Of course, the conceit is that he will walk to Heathrow Airport, then from JFK to downtown NY: there will be "only the mute, incurious interlude of a club-class seat" in between. He notes that on a previous attempt to walk all the way into Heathrow airport he "reached the road tunnel that plunges beneath the runways and into the terminal complex, only to find the following sign: "No pedestrian access. Go back to the Renaissance." "

Anyway, my ride was aimed not to reach the airport itself, but to bypass it. I want to explore more of North London by bike. To reach this area from Guildford, I can follow the Wey Navigation to its junction with the Thames at Weybridge, cross by ferry to Shepperton then follow the Thames towpath upstream to Staines. Glistening 10 miles to the North is the Grand Union Canal striking North, and providing a traffic free conveyance right around the top of London, a sort of cyclists M25, reaching exotic places such as Uxbridge, Hemel Hempstead,.... Watford. However, the M4 corridor interposes itself like an unfordable river. So I plotted a couple of routes to get across this corridor:

Route 1 (about 8.5 miles): leaves Staines by Moor Lane and stays 'inside' and close to the M25, picking its way through the 'hinterland' between the motorway and the airport to join the GUC at West Drayton, then using the canal towpath to reach Cowley Lock
Route 2 (about 11 miles): leaves Staines on the path beside the King George VI reservoir, then goes 'outside' the M25 via Colnbrook, and follows the Colne Valley Trail and Beeches Way, via Little Britain Lake to meet Route 1 at Cowley Lock.

A map of the two routes is below, with Route 1 shown in red and Route 2 in blue. Together they make a figure of eight, and I tried them out by starting from my car parked in Moor Lane, and cycling out via Route 1 (ie South to North) and back via Route 2 (ie North to South).

I thought Route 1 is the better of the two: it's shorter, more direct, largely traffic-free, and passes through surprisingly pleasant surroundings, including a 'Biodiversity' site within sight of Terminal 5, and Harmondsworth Park, which is the 'back garden' for the new BA HQ building. Here, an excellent network of cycle paths has been installed, many following the River Colne, which brought to mind Self's description of the stretch beside the River Crane on his walk to Heathrow...."snaking through the grass, the sentinel yews and tipping rowans, the massy oaks still in leaf." There is a short stretch of roadwork to reach the GUC at West Drayton, then the GUC towpath provides excellent cycling northwards.

Route 2 is longer, and the paths are less well suited to cycling. But both are pretty good.

I have annotated the map with notes on each route. I did it on a brilliant summers day, after a prolonged dry spell. The paths were in excellent condition for cycling, although at one point on Route 2, the path was totally overgrown with nettles (see photo below): I pushed through, not a pleasant experience in shorts. I imagine in winter both routes could get muddy Route 2 more so than Route 1.

If the proposed third runway for Heathrow goes ahead, then you can say goodbye to both these routes! But what are the chances of that happening?