THE UNLOST RIVERS OF LONDON Cannon Brook Northwood → Ruislip Common → Ruislip (2½ miles)
[Cannon Brook → Pinn → Colne → Thames]
Here's a short stream skirting Ruislip which I thought I'd never heard of, that is until I got to the famous bit and then thought "oh of course". For narrative reasons I intend to walk upstream, climbing from Ruislip's HS2 edgelands to Northwood's Iron Bridge.
Cannon Brook enters the River Pinn just north of Ruislip Golf Course, which is currently sealed off having been conscripted for use as a massive worksite for the tunnelling of the West Ruislip portal. Several local footpaths are either severed or on diversion, but the confluence is just far enough away not to be disturbed, and just about visible if you crouch through some trees in the corner of a meadow off Glenhurst Avenue. The nearby footbridge follows the alignment of Clacks Lane, a medieval trackway that HS2 has kindly left open, and which continues across a scrubby field to a shady track approaching the outer edge of Ruislip. The immediate area is a patchwork of small meadows, the next accessed over a stile beside the entrance to Old Clack Farmhouse, an isolated six-bed timber-framed Tudor bolthole. It's all very pleasant.
The last footbridges over the Cannon Brook are a concrete slab and a modern ribbed alternative better able to support passing machinery. The Hillingdon Trail crosses the former, this fine long distance footpath choosing to shadow the Cannon Brook during its fourth waymarked section. The stream is languid here, maybe two metres wide and heavily overhung with foliage. It also has a nearby artificial neighbour, the Ruislip Canal Feeder, which the Trail nudges across to follow next. This was dug in the early 19th century to supply water to the Grand Union Canal at Hayes seven miles away, a distance which proved the project's downfall because the gradient was pitiful and the supply thus unreliable. The channel's dry today, but you can still see a couple of very low bridges along the back path between two local schools.
The rural chunk ends here at the edge of the Green Belt as the outer nub of Metro-land intrudes. The houses in the middle of Ladygate Lane are a postwar addition on former allotments, the closest resident to the Cannon Brook being a proud soul with a Union Jack hoisted in the garden and a huge Middlesex flag flapping across the front porch. An Environment Agency sluice sends the Cannon Brook briefly into a culvert, this where it joins up with the delightfully named Mad Bess Brook, so called because it drains the delightfully named Mad Bess Wood. Meanwhile our stream has become the focal point of townhouse development along Wallington Close, the luckiest houses facing a preserved stripe of green and blue crossed by a single brick bridge. I have never seen so many signs on back gates saying "My Dog Bites And I Hope It Does", or words to that effect.
Howletts Lane is another suburban road on a former rural alignment, and here the Environment Agency maintains a water level gauge just in case flooding might be imminent. It very much isn't now, but this piddly stream very much topped three feet on 23rd September 2023. Slip down the side of Minnie's Hair & Beauty and a broad green corridor separates houses from risk - a delightful local resource and a proper playground for any adventurous youth permitted to leave the house. At one point a ridge of brambly earth dips down to a damp ditch spanned helpfully by planks and thick branches, should you be nimble enough to nip across. The final stretch before the river emerges from a concrete pipe is particularly incongruous because you can step down and walk along a perfectly flat gravel bed devoid of any water, as if a significant flow has simply ceased flowing.
We've reached CannonBridge, the point where the main road from Ruislip to Rickmansworth stops being Bury Street and becomes Duck's Hill Road. This river crossing was first recorded as Canons Bridge in the 14th century, it's thought because the land hereabouts was owned by a widow called Lucy Canon, and only in much more recent times did the bridge give its name to the brook passing through. See the 2004 Journal of the Ruislip, Northcote and Eastcote Local History Society for fuller details than you could possibly need. Cannon Bridge Farmhouse is timber-framed and potentially 16th century, and to continue to follow the river we need the footpath up the side. This leads into Park Wood, a fabulous expanse of thick broad-leaved woodland, although we're only threading through one brief oaky corner before emerging on the flank of a long sloping dam... and oh of course!
This is Ruislip Lido, Hillingdon's finest recreational resource, which was created by damming a river and that river was the Cannon Brook. In 1811 the Grand Junction Canal Company bought 60 acres of woodland, also a row of cottages, and flooded them to create a reservoir to feed the aforementioned canal. It ultimately failed, as also aforementioned, and in 1933 an entrepreneur repurposed the reservoir as a lido instead. The opportunity for outdoor swimming was augmented by rowing boats, sailing and water-skiing, also a miniature railway round the perimeter and more recently an artificial beach you're not allowed to paddle off. I can confirm that the Lido remains impressively busy in the school summer holidays as parents pile in with gleeful children, some patiently lugging trolleyloads of picnicgear, none of whom realise they're crossing a dam on a very minor river.
The Cannons Brook flows out of the Lido through a grille in the southeast corner, as necessary, and flows in at the top end near Haste Hill station. In 1990 volunteers at the Ruislip Lido Railway added a proper culvert beneath the tracks, suitably dated, whereas those on foot can only cross via a single level crossing (listening out for steamy whistles as appropriate). Several tiny tributaries merge here, one branch descending from the heights of Copse Wood and the remainder draining the adjacent golf courses. To follow the longest take footpath R38 between the derelict pump house and a patch of fenced-off wetland to emerge beside the 16th fairway. Alas this thin water feature soon disappears into private golf territory, a shallow ditch between pristine lawns crossed by a dozen tiny footbridges to permit the passage of players and trolleys.
To reach the heights of Northwood bear right by the enormous patch of Himalayan balsam and then trace the edge of fairway number 12, so close that they've had to erect a enormous mesh screen to protect ramblers from flying balls. Haste Hill's clubhouse is at the top of the slope, complete with inbuilt Bombay Chow brasserie where players can enjoy authentic Indo-Chinese cuisine or perhaps, if they arrive early enough, a Full English breakfast. The Cannon Brook is already flowing freely beneath its uppermost footbridge, lusciously fern-fringed, and puts in a first appearance behind the electrical substation on Lees Avenue. Contours suggest it once sprang from higher ground near Hillside Primary School but modern maps launch it from the Metropolitan line viaduct at the foot of Northwood High Street instead.
You'll only ever walk the Ruislip Lido stretch, I know, but isn't it good to know where the river that feeds it goes on the remainder of its journey?
