You haven't been everywhere London has to offer until you've seen Flash Lane Viaduct. This early 19th century engineering triumph hides less than a mile from the edge of London, in Whitewebbs Park in the borough of Enfield, and is an official Scheduled Ancient Monument.
Score yourself ten London Points if you know where Whitewebbs Park is. Give yourself eight points if you can pinpoint the village of Clay Hill, and know which bus takes you there. Award five points if I have to tell you we're inbetween Crews Hill and Forty Hall, and that helps. And make do with a bonus point if you had to look up Enfield on a map.
The New River is an early 17th century engineering triumph, a 40 mile canal carrying drinking water all the way from springs in Hertfordshire to fields near Clerkenwell. But because it had to work by gravity alone it followed a contour, and that made it exceptionally twisty, and the biggest twist was at Whitewebbs. To cross the Cuffley Brook required a hairpin bend well three miles in length, with Flash Lane near the tip.
Lengthy wiggles are inefficient, so in 1820 the New River Company decided to build a viaduct to chop the tip off. They came to Bow and paid £252 2s to Hunter and English to build a cast iron aqueduct wide enough to cross the Cuffley Brook. The aqueduct would be 18 feet wide, comprising four parallel sections bolted together, sealed with lead and lined with puddled clay. It was to be supported on two brick piers, allowing the stream to flow unhindered underneath while the New River was diverted across the top. Hey presto, one shortcut.
But the aqueduct barely lasted 30 years. In the 1850s the New River Company invested in pumping stations, allowing them to build a longer more complex viaduct the other side of Forty Hall and so chop off the entire Whitewebbs Loop. Shorter journey, less leakage, higher profits. And so the former waterway became redundant, the Flash Lane Viaduct fell into disrepair, and adjacent tree roots were left alone to do their worst.
The first improvement came in 1968 when the Enfield Archaeological Society excavated the trough, and two subsequent English Heritage grants (in 1998 and 2010) have effected fullrestoration. In the latest round the aqueduct was cleaned, a protective coating was applied, the brickwork repaired, some graffiti removed and the railings fixed. It looks a little more overgrown now at either end, and the former route of the New River isn't especially clear, but it is a proper quirky structure to stumble upon in the middle of the woods.
A splendid information board reveals more about the viaduct then we normally deserve, including an aerial photo, cross-sectional diagrams, before-and-after photographs, a map and a full history. A gate leads through into the aqueduct area proper, although walking down the bank and onto the ironwork isn't encouraged. A fresh footpath crosses the bridge beside the trough, then follows the Cuffley Brook downstream, affording sylvan views back towards the brickwork. How strange that the capital's drinking water once flowed through this remote woodland glade.
To find the aqueduct, take the rare-as-hen's-teeth W10 bus from Enfield and alight in the hamlet of Clay Hill, close to St John's church. Flash Lane begins opposite the recently-closed Fallow Buck pub, passing a string of secluded homes before continuing downhill as a muddy bridleway between paddocks and private woodland. The owner of the aforementioned woodland loses no opportunity to remind passers-by that the land across the barbed wire is Private Property Trespassers Will Be Prosecuted No Fly Tipping No Fly Grazing. Ten minutes gets you to the aqueduct.
On the far side this ancient track rises up through Whitewebbs Woods, a glorious sprawl of hornbeam and oak, ideal for a crunchy autumn stroll. I met absolutely nobody, and it was splendid. Head off piste through the trees and you'll stumble upon London's remotest TobyCarvery. Continue ahead to Whitewebbs Lane to reach The King and Tinker, a Jacobean pub with a set of stocks in its beer garden. Or go find the Whitewebbs Museum of Transport, if it's a Tuesday, based inside a former New River pumping station. Secret Hidden London is always worth exploring.