NETPark's real test was never whether it could attract start-ups. Plenty of science parks can do that. The harder test is whether the companies that grow up on-site stay there once they could afford to leave, and on that measure, twenty years in, NETPark is starting to pass.

Filtronic, the Sedgefield-based RF specialist and SpaceX's largest UK supplier, chose in 2026 to fund its own £200m-capacity headquarters on the park rather than relocate somewhere bigger.

SEEDS, a graphene materials company that arrived in 2014, has just expanded into new Phase 3 buildings to begin commercial production rather than move elsewhere to scale up.

Kromek, the park's original tenant, went from three staff to an AIM-listed company without leaving Sedgefield at all. That pattern, not the headline count of 40-odd tenants, is the clearest evidence NETPark has that its model works.

NETPark at a glance

Durham County Council took the former Winterton Hospital site into public ownership in 2000, already planning to remediate it, and use it to attract the kind of high-value manufacturing and engineering employment the wider area had been losing for two decades. The project formally launched in 2001. NETPark was officially opened by then prime minister Tony Blair on 23 July 2004 .

The choice of Sedgefield was not incidental. CPI's own account of the site's history points to the closure of the nearby Fishburn Coke Works in 1983, which had employed the large majority of local men, as the kind of economic shock the area was still recovering from two decades later. A council-owned science park on a remediated brownfield site was, in that context, a direct attempt to replace one kind of industrial employment with another.

CPI, a UK innovation and scale-up body with sites across the North East and beyond, was an early strategic partner and remains the biggest single presence on-site aside from the tenant companies themselves. It now operates several National Innovation Centres at NETPark, covering printable electronics, formulation and healthcare photonics, and was a founding partner of the High Value Manufacturing Catapult.

A science park's hardest job isn't incubating a company, it's keeping one. Cheap early space and shared kit will get a start-up through its first few years almost anywhere. What NETPark has been testing for two decades is whether a company that grows past that stage, and can afford its own site wherever it likes, still chooses Sedgefield.

Kromek, a Durham University spin-out, was the park's first tenant, arriving in 2004 with three staff to develop radiation and biological detection technology. It is now listed on London's AIM market, selling radiation detection products into medical imaging, security screening and nuclear markets in the UK and the United States, and it never left the site it started on.

Filtronic is the more recent and more visible version of the same story. The Sedgefield-based RF specialist, already covered by Review North, moved its manufacturing and R&D operations to NETPark in 2014 and its registered office there in 2022. In February 2026, it opened a new 44,000 sq ft headquarters and manufacturing facility on-site, funded entirely from its own operating cash flow and sized to support more than £200m of annual revenue, roughly four times its most recent turnover. Filtronic chief executive Nat Edington said the investment gave the company "the scale, capability and resilience needed for our next phase of growth."

Filtronic was also the first company to commit to Phase 3, occupying a custom-built site as the expansion's anchor tenant. A company that supplies SpaceX and builds components other specialist manufacturers struggle to replicate could plausibly have built anywhere. It built in Sedgefield.

SEEDS, short for Sustainable Energy Efficient Designed Structures, the graphene materials company's confirmed legal name, is the newest data point. It develops "Morpheus", an engineered graphene interface layer used in microelectronics, aerospace, batteries and renewable energy components, alongside printable graphene-based supercapacitor products for defence, drone and vehicle power applications.

Founded in 2013 by chief executive Jason Chehal, it moved to NETPark in 2014 and in 2026 expanded into new Phase 3 space, branded Argonaut Labs, to move from small-batch research production towards commercial-scale output, working towards a target of ten times its current production capacity. Chehal said NETPark provides "the complete ecosystem we need, world-class facilities, strong academic links and direct collaboration with CPI."

Three companies is not proof of a durable cluster. But three companies at three different stages, an AIM-listed detection specialist, a manufacturer scaling into capacity for more than £200m of annual revenue and a materials company moving from lab to commercial production, all choosing to stay rather than leave, is a more specific and more testable claim than "NETPark is a success." Business Durham's own account of the expansion names Filtronic and SEEDS among just four companies it highlights as the site's clearest results, which suggests the site operator reads its own record the same way.

Beyond the three companies above, NETPark's tenant base runs to more than 40 companies, working across compound semiconductors, satellite applications, healthcare photonics, printable electronics, formulation science and advanced materials.

Named tenants identified include PolyPhotonix (photonic medical devices) and Pragmatic Semiconductor, a University of Manchester spin-out. Two more, aXenic and Dyman Advanced Materials, are named by Business Durham itself alongside Filtronic and SEEDS as the expansion's four headline company examples. aXenic, a space communications and optical components specialist backed by Maven Capital Partners, spun out of the fibre-optics group Finisar and has marked ten years on-site. Dyman, a synthetic diamond materials manufacturer, secured £882,000 of investment in 2022 to fund its next stage of growth.

The site also hosts three national Catapult centres, the High Value Manufacturing Catapult, the Compound Semiconductor Applications Catapult and a North East Satellite Applications Centre of Excellence. These are run by their own national bodies, not by NETPark itself. CSA Catapult, for instance, was established by Innovate UK in 2018 and simply has a presence at NETPark, correcting an earlier, unverified Review North claim that Business Durham ran these centres directly.

Alongside them sit CPI's own National Innovation Centres for printable electronics, formulation and healthcare photonics, and Durham University's own research and enterprise presence on-site through its Centre for Advanced Instrumentation and the Orbit enterprise zone.

That density of shared infrastructure, cleanrooms, testing facilities, specialist equipment that no single small company could justify buying alone, is the actual mechanism behind the retention pattern above. It is easier to stay somewhere that already has the facility you need next than to build it yourself somewhere else.

Phase 3 is the clearest test yet of whether that mechanism can keep working at a larger scale. It is also not one single contract but a multi-year, multi-tranche programme, which is part of why published figures for its cost don't all agree. Business Durham's own current account of the whole expansion puts the total investment at £100m, adding 285,650 sq ft of laboratory, office and technical space.

The clearest breakdown of any single component comes from a North East Mayoral Combined Authority decision report covering just one tranche, three units on what it calls "Zone 1". Durham County Council has itself put in £48m of its own capital already, plus a further £24m committed to one of the three units. The North East Investment Zone added £11.26m of capital funding alongside £1.77m of local transport match funding for the same tranche, which is due for practical completion in August 2026, with its full outcomes, 400 skilled jobs on that specific zone, due by March 2032.

None of the documents found add these component figures up to £100m explicitly, but Durham County Council's own £72m of committed capital across earlier and current phases gets most of the way there once other tranches and private investment such as Filtronic's building are included.

NETPark was designated one of only two Growth Sites in the North East Investment Zone in January 2024, alongside a location on the River Tyne Corridor, giving it priority access to a flexible co-investment fund carrying £160m of government funding over ten years as part of the North East's wider devolution settlement.

The projected returns, once Phase 3 is fully occupied, are large. Durham County Council expects up to 1,250 additional high-value jobs on-site, a further 2,200 in wider supply chains and £625m added to the North East economy over ten years. These are projections tied to full occupancy, not figures already achieved.

North East mayor Kim McGuinness said NETPark "has become a driving force for attracting national and international businesses in Durham and the North East." Amanda Hopgood, Durham County Council leader from 2021 to 2025, said at the time that "the council took the bold decision to allocate land to establish a science park in County Durham" twenty years ago, a decision NETPark's own material now frames as the basis for a longer-term ambition to become a global hub for materials integration. Hopgood has since become the separate, ceremonial Mayor of Durham; Andrew Husband is the council's current leader.

The retention pattern above is real, but it currently rests on a handful of companies out of more than 40 tenants. Whether Phase 3 broadens that pattern, filling with a wider spread of scaling companies, or mainly builds more space around the same small set of flagships, will say more about the durability of the model than the last twenty years did.

The clearest single test of that is still conditional. Lockheed Martin has proposed an £85m satellite assembly, integration and test facility at NETPark, reported to create up to 500 jobs, but it remains a proposal, not a committed investment. It sits alongside a separate, larger Lockheed Martin commitment of £100m and up to 2,000 jobs across a wider UK space hub programme, a different figure that shouldn't be read as describing the NETPark site specifically.

If the NETPark facility goes ahead, it would be the clearest evidence yet that the site's specialisms, RF, compound semiconductors and now satellite manufacturing, are becoming hard to replicate elsewhere in the region. If it doesn't, that tells its own story about how far the cluster has actually matured.

There is also a supply-side question behind all of this. NETPark's growth, and Lockheed Martin's interest, are both tied to the development of the North East Space Skills and Technology Centre at Northumbria University, intended to build the pipeline of technicians and engineers a bigger site would need. Public investment can build the buildings faster than a region can train the people to fill them, and which of the two ends up as the constraint on Phase 3 is not yet answerable from published material.

The public funding case is easier to assess on its own terms. Durham County Council took on a remediation cost the private sector would not have carried in 2000, and two decades later has a fully tenanted, revenue-generating site with a public company and a nine-figure private manufacturer on it. Whether the additional tens of millions now being committed to Phase 3 produce a proportionate return depends on the projected 1,250 jobs and £625m of added economic activity actually materialising, figures that are still projections rather than results.

What is NETPark? The North East Technology Park, a science, engineering and technology park in Sedgefield, County Durham, built on the site of a former NHS hospital. It opened in 2004 and is now home to more than 40 companies.

Who owns NETPark? Durham County Council, which took the site into public ownership in 2000. Business Durham, the council's business support arm, manages it day to day.

What does NETPark specialise in? Compound semiconductors, satellite applications, healthcare photonics, printable electronics, formulation science and advanced materials, supported by three national Catapult centres and CPI's National Innovation Centres on-site.

What is NETPark's clearest evidence of success? Not the headline company count, but retention. Kromek, Filtronic and SEEDS have each grown from small beginnings to significant scale without leaving the site. Filtronic's self-funded £200m-capacity headquarters, opened in February 2026, is the most visible example.

What is Phase 3? NETPark's current expansion, backed by public infrastructure funding now reported at £100m and North East Investment Zone Growth Site status. Filtronic is the first company to build on the new land; SEEDS has expanded into new Phase 3 space to move into commercial-scale graphene production.

Is Lockheed Martin building a facility at NETPark? Not yet confirmed. An £85m satellite assembly, integration and test facility, creating up to 500 jobs, has been proposed but not committed as of this piece's last update.

How much public money has gone into NETPark's expansion? Business Durham's own figure for the whole Phase 3 programme is £100m. The clearest documented component is Durham County Council's own £72m of committed capital across earlier and current tranches, plus £11.26m of North East Investment Zone funding for one specific tranche.