The brutal reality of the Silk Stream Bridge
Artist’s impression by bridge architects, Makower Architects
** This report was first published in September 2021. It has had a few minor revisions and updates in the years since **
Background
Due to be built by Barratt London as part of the Hendon Waterside regeneration programme in North West London, a controversial new 186-metre footbridge is set to cross the protected north marsh of the Welsh Harp (Brent Reservoir) — a Site of Special Scientific Interest (SSSI) since 1950. Its construction will destroy a large area of existing wetlands in order to link a new housing development with playing fields.
To facilitate the scheme, Barnet Council compulsorily purchased a corridor of the north marsh from reservoir owner Canal and River Trust, and in 2018 granted planning permission to Barratt London for the construction of the bridge with conditional approval by Natural England pending final designs. This was against a raft of objections from leading bodies including London Wildlife Trust, Canal and River Trust, RSPB and even Natural England itself.
Using new evidence and archive photographs, this 2021 report shows why the planning process was flawed, supporting evidence was misleading and the bridge should not go ahead as planned.
The misleading planning documents
“The new pedestrian bridge,” says the official description in the original planning documents, “will be located in woodland to the north of the reservoir and will span the Silk Stream which is one of two watercourses that flow through the reservoir. The bridge will be c. 186m in length and facilitate pedestrian access between the West Hendon Estate and open space to the north west. It will be constructed of prefabricated units, suspended on paired steel piers which themselves will be stabilised by piles driven into the woodland floor.”
Drawing of new footbridge from planning documents
Looking at the bridge route (shown above in pink with the construction site outlined in red), it would seem obvious that 90% of the bridge passes over land (the ‘woodland’ referred to in the planning description, shown in white), with seemingly little impact on the reservoir (in blue).
So what’s the problem?
The problem is that in the real world much of the land depicted is not land at all, nor even ‘woodland’, but the forgotten overgrown wetlands of the north marsh SSSI bird refuge — precious legally protected habitat built from 1985-1990 with public money, but left unmanaged for decades by statutory bodies potentially in breach of environmental law.
The shape of Welsh Harp reservoir and its north marsh bears no relation to this drawing. In fact, such is the extent of open water, you could even take a boat into sections shown as dry land.
You might even be forgiven for thinking the drawing was deliberately created to give the impression the bridge will mostly cross over a nondescript area of land with little impact on the reservoir or SSSI.
Aerial impression from the planning documents
In this second image (above) also from the planning documents, again the bridge is made to look as though it passes through dense woodland, with the reservoir further to the south east.
In fact, the reservoir — although now heavily overgrown in places with colonised vegetation — stretches right up as far as the large white square warehouse (below the words ‘W Hendon Broadway (A5)’). Chronic neglect, silting and willow encroachment has allowed a canopy to develop over the landscaped wetlands in this area, making it look like woodland from above. It is not. It is legally protected open water, islands and screened breeding bird habitat that, owing to natural succession — allied to decades of poor stewardship — has now morphed into a jungle of colonised willow and giant hogweed, orphaned pools of water, and silted-up canals.
And yet, despite its protected wetlands origins, the Barnet Council Decision Notice granting approval for the bridge — and the influential executive summary of the Ecological Assesssment written in support of the original plannning application — each use the broad, and arguably misleading single term ‘woodland’ 88% of the time to describe the area.
It is not until page 19 that the Ecological Assessment admits, “The woodland floor comprised a matrix of pools and wet channels with trees and vegetation growing on islands of slightly higher ground.”
We say, of course it does. It is not a woodland floor at all. It is the neglected wetlands and bird refuge of a protected SSSI.
The forgotten reality
Looking at this aerial photo taken in the early 1990s, the open water and islands and lagoon of the original SSSI remodelling — built with major funding from the GLC to support wildlife and a nationally important breeding bird population — clearly stretch to the top of the image.
Aerial photo taken shortly after SSSI wetlands were created in 1985 . The corner of the warehouse in previous image is just visible at the top of the image.
It is not woodland, not even wet woodland, but thriving wetlands.
To make it even clearer, the three photos below show the north marsh looking towards the mouth of the Silk Stream before and after completion of habitat and management works in the 1980s.
In all, the protected wetlands SSSI habitat with its islands, pools and open water is clearly visible, and yet the Barnet Council Decision Notice and the Ecological Assessment make no mention of it, successive authorities have neglected it and the proposed footbridge will cut across it.
The real impact
The Ecological Assessment used in the planning application asserts:
“Embedded design features include siting of the bridge as far north as practical to ensure a substantial woodland buffer between the bridge and the open water of the northern arm of the reservoir”.
Superimposition of new footbridge across actual shape of SSSI north marsh wetlands.
The superimposition image above shows this is not true; the bridge will actually pass right through the neglected northern arm of the reservoir across a SSSI bird refuge in desperate need of restoration. There is no natural ‘woodland buffer’, only overgrown protected wetlands.
On their website, the bridge architects Makower Architects even go so far as to inexplicably rename this part of the reservoir ‘the flood plain of the Silk Stream’; they also call the Welsh Harp a ‘nature reserve’ but fail to mention the reservoir and its boundary has been a SSSI since 1950, and claim the bridge ‘runs around’ it.
We say planning permission for this pedestrian bridge has been granted using grossly misleading information and the real impact has not been accurately represented to the public.
Is it too late to save the wetlands?
We say no. The next four photographs taken in May 2021 clearly show that thirty years on, large areas of open water and most of the landscaping still exist, if overgrown and hard to reach in places due to colonisation. It is certainly not the littered nondescript woodland and dry land used to make the case for the route of the bridge.
Abandoned north marsh wetlands, May 2021
To construct a 186-metre bridge over it - with attendant irreversible ecological damage, and a future of human disturbance and almost certain fly-tipping and antisocial behaviour - would only add insult to years of neglect and environmental injury.
Abandoned north marsh wetlands, May 2021
What’s at stake?
The Welsh Harp (Brent Reservoir) has been designated a Site of Special Scientific Interest (SSSI) since 1950, notified primarily for breeding wetland birds, the diversity of wintering waterfowl and rare fenland plants.
Many species of waterbird have seen local breeding numbers drop by as much as 80% since 2000. Many rare plants have disappeared. Thirty years of habitat neglect by successive statutory bodies has without doubt contributed to this.
And yet none of the three landowners — Barnet Council, Canal and River Trust, Brent Council — hold an official list of protected flora and fauna, or a map of invasive species, or robust plans to reverse falls in protected bird numbers. Barnet Council don’t even have an ecologist, a biodiversity officer or any biodiversity plan. In the meantime the north marsh SSSI bird refuge — once a haven of islands, pools, scrapes and quiet breeding areas — has been allowed to become a lost outpost.
(Footnote: In the wake of this report, Barnet Council appointed both a biodiversity officer and ecologist in 2022; and the INNS Mapper is now being used to slowly build up a picture of invasive plants.)
Abandoned North Marsh Wetlands, May 2021
In spite of this, the Ecological Assessment used in the planning application manages to conclude: “Based on implementation of the Construction Method Statement and delivery of the embedded mitigation and enhancement measures no significant effects on important ecological features will occur as a result of the construction and operation of the Silk Stream pedestrian bridge.”
We have to ask how this can be a realistic conclusion.
Abandoned north marsh wetlands, May 2021
Time for change
Notwithstanding the destruction of a large section of one of London’s premier SSSIs, it is also clear times, priorities and public sentiment have changed since planning was approved for the footbridge in 2018.
Not only has the COVID-19 pandemic of 2020 ushered in a new age of green awareness and mental health concerns driven by a public keen to re-engage with nature, but the UK parliament declared a climate emergency in May 2019 with over two-hundred councils pledging to work with partners and local communities on tackling key issues such as decarbonisation and improved biodiversity. Wetlands are now considered central to future-proofed urban planning, absorbing heat in summer and acting as a sponge in winter. These alone should make Barnet Council and Barratt London seriously reconsider the current proposals for the Silk Stream Bridge.
What’s more, most of the residents newly installed in the Hendon Waterside redevelopment have no idea about this bridge; their opinions have not been polled as the bridge was approved before they moved in. Who says they want direct access to football pitches? Maybe they’d like to save a protected 70 year-old SSSI. Maybe they’d be prepared to walk a little further along a different route and have both.
As it is, for most residents the bridge will only save four minutes on the same journey along West Hendon Broadway to the same end point.
Many might also deem a well-lit walk along the road as arguably safer, when compared with a 186m bridge, with low-level lighting, no clear view to its opposite end, through an extremely quiet wooded part of the reservoir. Are Barnet Council and Barratt London really prepared to wreck a historic protected wetlands in order to save residents four minutes on a bridge that might not get used much?
If the bridge goes ahead as planned, it could quickly prove a huge misjudgment as an amenity, and the northern arm of the Welsh Harp — a fragile wildlife habitat for protected breeding species since 1950 — would be at further risk of becoming little more than an ornamental lake for private housing.
Is there a solution?
At the time of the planning process an alternative less invasive northern route for the footbridge - a mixture of footpaths and small bridge over the Silk Stream - was supported by Natural England, London Wildife Trust, RSPB and local conservationists, but it was rejected. We remain in support of this route - less glamorous, but non-destructive.
Yet, if a clear span bridge is still deemed essential to the over all regeneration of the West Hendon estate and abandoning it completely is not an option, we say yes, there is a better solution.
Possible alternative routes minimising impact on wetlands
We propose a new solution in the illustration above — a raised bridge to meet current planning conditions, but through a revised corridor, and either curved or angled to swerve around the wetlands. (The open water of the wetlands is clearly visible between the tree canopy in this 2021 Google Maps image.) Saving the integrity of the SSSI wetlands should be ample justification for a revised bridge corridor and new span design.
The wetlands — long overdue rehabilitation — could then be restored as part of the ecological mitigation works due after construction, and align with other Government-approved Blue and Green Recovery programmes and climate emergency targets across the UK.
Conclusion
We’ve heard some say that surely Natural England has vetted the whole scheme and it must be ok. It is true to say the regulator has still to insist on yet-to-be-determined ecological mitigation measures once Barratt London submit the final designs, but crucially we believe, like many people, Natural England was not appraised of the full damaging nature of the scheme during the planning process. We believe that it has been caught out by the true scale of the destruction, and as a result is trapped on the back foot. Whether it has the muscle to insist on measures truly representative of the damage that will be caused is yet to be seen.
It is difficult not to conclude the north marsh wetlands and the full footprint of the reservoir either went completely unrecognised during the consultation and planning phase — which is in itself a major ecological and historical oversight — or were imaginatively represented as woodland and partial wet woodland in an effort to draw attention away from their significance.
We urge Barnet Council, Barratt London and Natural England to now acknowledge the presence of the neglected 1985 wetlands and re-assess the sheer scale of the ecological damage that will be done by the proposed bridge, and we vigorously recommend a planning permission amendment is issued that either abandons the project or significantly alters the bridge’s alignment.
If a case is made by Barnet Council and Barratt London to retain the existing route regardless of the information provided in this report, we urge Natural England to use their power of veto to impose the strongest possible mitigation conditions prior to construction that must be implemented by Barratt London after the bridge is completed.
This must mean wide-ranging improvements and net biodiversity gain both around the bridge and in other parts of the north marsh to fully compensate for the previously unacknowledged vast loss of legally protected habitat that this report brings to light.
2025 Update
As of September 2025, the bridge still remains unbuilt. As the area sits in limbo, invasive species have taken a grim hold of the woodland around the Silk Stream to the point where eradicating them (a cornerstone of the planning permissison) may now prove almost impossible.
Other restoration projects around the north marsh - for example, the urgent de-silting of the reservoir around the mouth of the Silk Stream by Canal and River Trust - are being forced into a holding pattern until the scale of the bridge project finally reveals itself. If the bridge itself weren't destructive enough, the wait for it is now standing in the way of other meaningful progress.
In contrast, following a future habitat proposal from Cool Oak, Canal and River Trust is now set to restore approximately two hectares of the north marsh away from the bridge site, re-instating old canals, islands and reed beds on the western side with major third-party funding and existing S106 monies.
It proves that the will is there to breathe new life into the SSSI - something several Barnet officers have told us would never happen.
We have to ask why the same cannot be done for the rest of protected north marsh, instead of subjecting it to the unnecessary and irreversible destruction the bridge will bring.
Over a year ago, and in light of our report, stakeholders were promised Barratt London were issuing a material amendment to the bridge design (‘a lighter version’, we were told), which would have re-opened debate and perhaps shone a light - 15 years on - on how dated and unnecessary the whole idea has become.
In recent years, key connected infrastructure has fallen away: the £18 million West Hendon Playing Fields regeneration has been effectively mothballed with only a fraction of it now due to be spent on renewal; the proposed primary school at Hendon Waterside, which was expected to provide a regular flow of users of the bridge as children were ferried to the playing fields, has been abandoned. Even the dream of an appealing treetop walk is now ludicrously far-fetched as most of the trees in the area have been found to be tall unstable willow in wet footings, prone to falling without warning. Anything in the bridge corridor will need to be felled. What will be done about the risk of trees falling on the bridge from the southern side outside the build-zone is unclear.
Residents are also starting to realise how much they might have to pay in increased service charges to maintain what will be in effect a huge - and most likely little-used - new private bridge for public use with attendant anti-social-behaviour and personal-security risks. A recent straw poll of residents showed none are even aware of the imminence of the new bridge, let alone that they might have to pay for it, and those that are aware are incensed.
Surely it is time that Barnet Council finally drew a line under this dinosaur of a scheme, used their existing statutory powers of veto, and absolved Barratt London of the need to build it by amending the curtilage of the project and perhaps even handing back the compulsorily-purchased corridor of land through which the bridge would have passed to Canal and River Trust, who could then spearhead the full restoration of protected habitat of the north marsh.
Certainly if it becomes known that the council could have stopped a project that gets little use, invites trouble, partially destroys a famous SSSI and results in long-term service charge hikes for thousands of local residents, we suggest it might not be a good look for any incumbent administration; especially, when a much cheaper and less invasive footpath and bridge across the Silk Stream, skirting the SSSI, has always been a heavily-supported option if a new greenway to the playing fields is deemed essential.