One of London's oddest open spaces can be found on the western edge of London, almost as far west as London goes, tucked inbetween Heathrow and the M25. A stripe of species-rich grassland fills the gap between the motorway and the airport perimeter road, about a mile in length and half a mile wide. Most of the week it's quiet like any other nature reserve, but if the wind's in the right direction and the runways are appropriately flipped then every couple of minutes the sky briefly roars.
This is the Heathrow Biodiversity Site, one of several peripheral spaces watched over by the airport to boost its green credentials. There are no hangars or hotels here, nor even any buildings, just hummocks of grass and thickets of trees alive with wildflowers, birds and other wildlife. But Heathrow Airport Holdings Limited aren't acting as eco-guardians purely out of the goodness of their hearts. They need wetlands to soak up the risk of flooding around their very large expanse of tarmac, and they also prefer nobody to live in the liminal areas where planes are loudest and at greatest risk of a crash. But mainly they're looking ahead because owning most of the surrounding land helps to make any potential expansion of the airport a heck of a lot easier. Whoosh!
The easiest way to get here is probably via the number 81 bus. You need to alight at the first stop after the village of Longford which is the last stop before the Greater London boundary, that's Moor Bridge. Expect the entrance gate to be obvious but not especially encouraging - no there's no public right of way but yes you can come in, just don't allow your dog to foul. A mud track then bears off south on an undulating path between grazed meadow and locked woodland, and all you need to know is that the Heathrow flight path crosses at the foot of the first brief dip where the wooden fence begins. Pick your vantage point - I prefer the grassy summit on the left - and if planes are landing from the west on the northern runway you won't have long to wait.
A steady convoy of planes can be seen approaching above the treetops, lights ablaze. As each approaches it grows larger and louder until it's above you, perhaps directly above, a tube of brightly-painted fuselage with all of its tray tables in the upright position. You can almost sense the pilots staring straight ahead thinking what's that idiot doing down there gawping in the middle of a field. As the noise peaks the aircraft descends further towards the edge of the field, then heads across the river and the boundary road to the end of the runway barely half a mile distant. If you get lucky with the angle of the sun the plane will be closely followed by its shadow sweeping across the clover, and I am inordinately pleased with my video depicting this.
The planes in the procession range from fairly small to occasionally very large, the latter being most likely to make you go wow as they swoop by. The larger planes also instigate turbulence, not immediately but maybe ten seconds after they've flown over, which manifests as strange whistling eddies in the branches of the trees. I only noticed it down by the fenced-off meadow called Orchard Farm, directly beneath the flight path, but it was certainly eerie like the sudden manifestation of a spirit or an invisible giant stepping through the leaves.
On previous visits I've found the biodiversity zone empty but on this occasion a pair of planespotters - father and son - were perched on the central hillock watching everything fly by. They'd brought chairs and various refreshments and were keeping tabs on mobile devices to confirm what was approaching next. Then as each plane arrived in the airspace in front of them, perfectly lit, they trained their enormous lenses and followed the aircraft for a few close-up seconds of pitch-perfect landing, or perhaps turbulent wobble. It's just the kind of thing spotters do at Myrtle Avenue on the opposite side of the airport when runways are switched, but generally in far greater numbers, so these two image-grabbers were enjoying a considerable amount of exclusivity.
This grassland used to be gravel pits and before that a patch of orchards just off the Great West Road. The M25 changed all that, careering down the Colne Valley via the path of least resistance (which was the flood plain of the river where sensible humans tended not to live). Following construction the area was relandscaped and nature allowed to take its course, with separate chunks of grassland connected via a single track weaving north to south. The southern end is even more remote, emerging by the roundabout that really is the westernmost point in London and there's no good reason for going there. But the animals that live here prefer visitor numbers to be tiny, hence the cheerful birdsong from the hedgerows, the bumble bees amid the dandelions and the fox prints in the earth.
When Terminal 5 was built a new spur of motorway was needed and this was built straight across the centre of the Heathrow Biodiversity Site. It stalks across the valley on concrete stilts leaving space for the Colne and the spine path to pass gloomily underneath, emerging into blinking artificial landscapes on either side. It's a reminder that even one of London's great rivers isn't immune to tampering when engineering demands, in this case because it had the misfortune to flow past an even greater airport.
Heathrow's most recent plans for a third runway would see the permanent diversion of the Colne via a new artificial channel further to the west, and the total eradication of this slice of grassland to make way for a pair of taxiways linking the old runways to the new. The Bath Road would be swallowed, the M25 sunk into a tunnel and the wildlife I saw would have to find somewhere else to be biodiverse, having all been sacrificed to the gods of international travel. But these expansion plans are so destructive across such a wide area that they'll only ever go ahead if political intent outweighs environmental pressures, which currently looks unlikely, so I expect the Heathrow Biodiversity Site will continue to be buzzed by low-flying aircraft for many years to come.
Maybe come one day and be wowed, but make sure that flights are landing in the right direction otherwise all you'll find is a quiet swathe of bees in clover.
