The Ealing stretch of the A40 starts outside Park Royal tube station. It'd be East Acton on the current boundary, but the original dividing line was Green Lane, now reduced to an alleyway up the side of the Piccadilly line. That's no great shakes, but my word the station building is magnificent, an art Deco confection with geometric shapes stacked in red brick, with the contrast between cylindrical ticket hall and clocktower a particular highlight. The adjacent shopping parade was erected in similarly streamlined style, now an odd mix of supermarket, Boden outlet store and boarded-up nightclub.
It's only a short walk to Hanger Lanetube station, not quite the architectural equal of its neighbour but still with an alluringly circular facade. Opened just after WW2 rather than just before, it was once the dominant feature at the crossroads where Western Avenue met the North Circular. The creation of the infamous Hanger Lane Gyratory in the 1980s saw the station marooned on a central island, so access is now via a tiled subway whose signage might leave you wondering where on earth the ticket hall is... until you spot it up one arm from the central atrium.
Here goes with the arterial slog. The A40 sweeps down from Hanger Lane into the valley of the River Brent, past a row of well-glazed houses on Greystoke Park Terrace and some allotments where St George's flags limply flutter. Nip into BrenthamMeadows for a brief break from the traffic, and take a peek at the not-quite scenic river curving beneath the main road in a concrete channel. This is also the point to check out what amazing object the Vanguard Self Storage company has on its roof at the moment. In the past it's been an artillery gun, a single decker bus or a Hawker Hunter jet, but currently it's a Tardis (if you're the Londonist muppet responsible for tweeting four-year old posts, take note).
The highlight of the entire road trip is, or ought to be, the Hoover Building. This Art Deco masterpiece was opened in 1933 for the manufacture of vacuum cleaners, with pillared glass facade and Aztec-style detailing. Tesco bought up the factory space in 1989, and now operate a improbable supermarket round the back, while the officeshavelaindormant (and decaying) for years. In a move that'll surprise nobody, they're now being transformed into 66 luxury apartments with contemporary interiors, bespoke kitchens and gated underground parking, in a postcode "yet to fully maximise its real estate potential". Mass scaffolding and one of the tallest cranes in Ealing mean that 2017 is not the ideal year to admire the building.
Perivale's 12th century flint church has been severed from the community by the A40, swallowed by a golf course and hidden behind a Premier Inn, which aren't factors conducive to a large congregation, so since 1972 it's been run as an arts centre rather than a place of worship. Last night at St Mary's Perivale you missed Grieg's Peer Gynt Suite, while the The Lipatti Piano Quartet are playing Mozart and Schumann on Sunday. Beside the petrol station is the equally unlikely sight of a shiny American diner, formerly StarvinMarvins, although the doors are bolted, the lights are off, the red leather chairs at the counter are empty, and a 2015 diary sits forlornly on the laminate.
For those on foot or two wheels, the A40 is quite difficult to cross, with a minimal number of subways, bridges or at-grade junctions. There's a rare set of traffic lights at Argyle Road, plus a footbridge by the railway near Perivale Park, which you'll have negotiated if you've ever walked the Capital Ring. Up on the embankment is the third least used station in London, South Greenford, or 'West Perivale' as the marketeers at the Hoover Building prefer to call it. Not much investment has been sprinkled at this lowly halt, which helps to explain why the signs outside still promise "All stations to Ealing Broadway/London Paddington", when in fact the service was cut back to West Ealing at Christmas.
Even though nobody would build homes facing onto a six lane dual carriageway today, ribbon development was very much in vogue when Western Avenue was constructed in the late 1920s and early 1930s. Residents of the appositely-named Leaver Gardens look out onto a verge of daffodils, a screen of trees and a series of crash barriers, and one house boasts a 'Corporation of Ealing' manhole cover in the pavement outside. Meanwhile guests at the Bridge Hotel may not be overkeen to discover that their rooms look out onto the Greenford Flyover (rather than the bridge the original pub was supposed to be named after, which is two miles away in Southall, except in 1937 the joint owner accidentally transposed the names when filling in the licence forms).
The next mile and a half of the A40 is actually rather pleasant to walk, thanks to the Northolt and Greenford Countryside Park which runs alongside. The footpath weaves behind a screen of trees beside the Greenford Lagoons, where tall grasses wave, before opening out into the more extensive Marnham Fields. Across the road is the striking AladdinTower, once part of a lamp factory (obviously), more recently requisitioned as a warehouse-sized branch of Dunelm, the soft furnishings company. Where the Grand Union Canal ambles through the park you could almost believe you were in the country, assuming you had your headphones on.
The 21st century highlight of the walk is Northala Fields, Ealing council's flagship post-millennial recreational project. There's a park and a cafe and a fishing lake, if that's your thing, but far more fabulous are the four conical hills made from half a million cubic metres of waste dug up during the construction of Wembley Stadium and Westfield. The tallest has a spiral pathway to the summit, at a wheelchair-friendly gradient, whereas the others are brief exhilarating scrambles. And the view is fantastic, there being nothing else of any comparable height around, my personal favourite being to the east (in the direction of the road just walked). From here central London's skyscrapers line up mostly unobscured by one another (apart from One Canada Square behind the Trellick Tower), currently with a burst of spring blossom in the foreground.
Northolt's TargetRoundabout is named after another huge traveller-friendly 1930s pub, this time transformed into a McDonalds, because scoffing burgers is safer than drinking and driving. From here the A40 descends into open country, not that you can see the golf course on the left, but Islip Manor Meadows are pre-eminent on the right. These scrappy inaccessible fields look like they ought to be prime candidates for extensive residential development, but are actually a wetland nature reserve with a diverse ecology, including sneezewort, devil's-bit scabious and the EU-protected great crested newt.
The Ealing section of Western Avenue halts suddenly several hundred yards before the Polish War Memorial, a far from ideal place for a walk to end, not that an arterial road is ideal for a walk in the first place. But even if you have the sense never to repeat all that I've done, an exploratory stroll from Greeenford to Northolt via the A40 wouldn't be the biggest mistake you've ever made.