THE UNLOST RIVERS OF LONDON Coppermill Stream Tottenham Hale → Stamford Hill (1¼ miles)
[Lea → Coppermill Stream → Lea → Thames]
The braided rivers of the Lea Valley are complex and hard to pin down historically because matters of navigation, water supply and flood prevention forced their inexorable evolution. The first Act of Parliament aimed at improving the river's course came in 1425, then in 1571 the River Lee Navigation Act authorised the creation of straighter cuts chopping off awkward meanders and the introduction of towpaths on both sides of the river. The sequential introduction of major reservoirs in the second half of the 19th century entirely redrew the map in the vicinity of Walthamstow, which is where we find ourselves today, and the Lee Flood Relief Channel brought further restructuring after WW2.
The Coppermill Stream is thus unusual amongst London's unlost rivers in that it didn't always exist and also used to be longer and is now an entirely artificial construct. It also doesn't bubble up from the ground, its source is water entering from the River Lea itself, and at the other end it either flows back into the Lea or ends up in a water treatment works and eventually comes out of your tap. That said there was once a copper mill here, the road that runs up to Walthamstow is Coppermill Lane and the filtration plant is Coppermills Advanced Water Treatment Works, a major facility that provides drinking water for 1½m households in East London. Let's just walk it shall we?
Today's Coppermill Stream begins amid the Walthamstow Wetlands, the reservoir-packed nature reserve opened up to the general public in 2017, which means I couldn't actually have walked this river ten years ago even if I'd wanted to. We're in the lesser-walked half of the reserve to the north of Ferry Lane, about two minutes from the road, where water overtopping the Low Maynard Reservoir tumbles noisily over a fenced weir. The reason for the artificial source was the construction in 1897 of the enormous Lockwood Reservoir, last and largest of the Walthamstow reservoirs, whose excavated footprint destroyed a former channel threading down from Tottenham Marsh. The footbridge that crosses the start of the stream is securely locked for reasons of biosecurity. A pylon stands sentinel. A thick appropriately-copper pipe suggests there's a lot more going on here infrastructurally than meets the eye.
The Stream, which feels more River, flows quietly behind a hedge for about 200m, but with occasional gaps in case you want to peer in. I'd like to apologise to the heron I disturbed here, twice, before it swooped off to eye up prey in quieter waters. The beer garden across the water belongs to the Ferry Boat Inn, a 200 year-old pub with pitched tiled roof which once catered to weekend Cockney merrymakers and is now more steak than ale. It faces Ferry Lane, once one of the very few places the Lower Lea could be crossed, and which still manages to cross six separate channels of water. If approaching from Tottenham Hale the first waterway you meet is the Pymmes Brook, then the full-on Lee Navigation (used by boats and ramblers), then two forks of the River Lee Diversion (the second of which once marked the boundary between Middlesex and Essex). The Coppermill Stream is number five and finally, on the very far side of the reservoirs, is the River Lee Flood Relief Channel. Do cross the road carefully.
The southern half of the Walthamstow Wetlands is better trod, especially by folk carrying fishing rods and/or binoculars. The Coppermill Stream sneaks in under the Goblin, or as we have to call it now the Suffragette Line, then runs briefly alongside the viaduct. Streamwalkers must instead negotiate the car park and aim for the Engine House, once a pumping station and now a visitor centre with an integral cafe offering. For an elevated view of the stream, and to look down on the heads of the latte-slurpers, head upstairs to the industrial chic viewing platform and keep your fingers crossed the outdoor terrace is unlocked. It wasn't yesterday. Alternatively the river flows right past the downstairs patio and underneath the bridge everyone has to cross to reach the main reserve, so you may well have soaked in the ambience of the Coppermill Stream yourself.
When I've been here before my eye's always been on the mighty reservoirs and thus not the river quietly threading inbetween. But here it flows, trapped between thin brambly banks, occasionally linked by sluices to the rest of the reservoir chain. Birds tend to prefer the larger waters, it has to be said, but a few ducks and moorhens prefer milling about on the Coppermill. Some local fly fishers prefer it too, taking up position on a narrow strip of footpath on the far side, but that's because they're allowed to walk past the signs that say 'Sensitive Wildlife Area Please Do Not Enter' and non-anglers aren't. A full half mile of the Coppermill Stream is enticingly visible like this, which is a lot better than many unlost rivers manage.
The large brick building streamside is called the Coppermill and sits on the site of a windmill built here four centuries back. In the 1800s it was purchased by the British Copper Company who built a watermill instead so they could transport copper ingots from Wales by sea (and by Lea) and roll the metal into sheets. This'll be when the name of the stream set in. The building was later used by the East London Water Company as a pumping station when their first reservoirs opened, hence the Italianate tower perched on top, and these days Thames Water merely use it as storage space. But visitors are welcome to step inside and climb to the top for a perhaps windswept view across the Warwick Reservoirs towards the Hackney/Haringey skyline. A new cluster of flats seems to have shot up every time I visit.
The Coppermill Stream is last properly seen as it flows out of the Wetlands behind a row of trees, now muted because a lot of the water has been funnelled off for filtration. It used to meander a lot here before the reservoirs were built but still passes under the railway line where it always did. Everyone else has to duck beneath the notorious Incredibly Low Bridge, headroom 1.5m, which was even more hazardous yesterday because it had almost entirely flooded. I assume every serious London psychogeographer has taken a selfie here. It's now but a very short walk (fork right!) to the mouth of the Coppermill Stream at Coppermill Bridge, or the overgrown remains of it. Originally the stream entered the Lea on the outside of a very squished meander but that's since been bypassed and the infill is now a private pleasureboat marina. Happy 10th anniversary.
