UK fusion prospectus confirms STEP’s engineering door is still open

Demo4, Tokamak Energy’s HTS demonstrator, reached 11.8 Tesla in testing ahead of STEP’s own magnet development

(Image courtesy of Tokamak Energy)

The UK government published its fusion investment prospectus alongside the Global Fusion Summit in London and a new UK-US agreement to explore linking fusion supercomputing efforts. Behind the market-sizing language is a detail worth the supply chain’s attention. More than a year after two consortia were shortlisted for the role, UK Fusion Energy has yet to appoint an Engineering Partner for STEP.

What the UK fusion investment prospectus reveals about STEP’s partner model

The prospectus’s own partnering diagram names three System Partner roles. UKAEA was appointed Fusion Partner, and ILIOS was appointed Construction Partner in March 2026, holding a £200m contract. Engineering is the one still open.

Additional system-level work sits outside that core three, though the prospectus reuses the same System Partner label further down the supply chain. Tokamak Energy was appointed Magnet Systems Partner in April 2026, delivering a £70m contract through its TE Magnetics division and built on the company’s high-temperature superconductor expertise. Dassault Systèmes was awarded a separate £30m contract covering part of STEP’s Plant Information Management System, also in April 2026. The prospectus says UKFE intends to approach the market for the Engineering Partner role, with near-term work delivered through a range of system partners in the meantime.

Why STEP’s engineering role is still open

The role has been open longer than the prospectus alone suggests. UKIFS shortlisted two bidders in January 2025, Celestial JV, led by Eni UK with AtkinsRéalis, Jacobs Clean Energy (now Amentum), Westinghouse and Tokamak Energy, and Phoenix (UK) Fusion Limited, led by Cavendish Nuclear with KBR and Assystem Energy and Infrastructure. UKIFS said at the time that both would enter what it called competitive dialogue, run alongside the construction lot that went on to produce ILIOS.

A December 2025 report by New Civil Engineer said the process had stalled, with UKIFS calling its own approach “not suitable” and expecting the competition to resume in a year or two, while construction procurement carried on unaffected.

A notice for a Systems Engineering and Whole Plant Integration Partner is listed on the government’s Find a Tender service, a preliminary market engagement exercise with supplier responses due by July 3, 2026. Nothing in the notice or the prospectus states whether it replaces the cancelled Engineering Partner competition. Read alongside the prospectus’s language about near-term work sitting with a range of system partners, it looks like a plausible next step, though not a confirmed one.

What the fusion investment prospectus leaves for suppliers to track

The prospectus doesn’t say when, or if, engineering delivery gets consolidated into one contract, and it never mentions SEWPIP by name. What it does offer is a working list of doors still open to suppliers, a Fuel Cycle System Partner, an Embedded Engineering Resources Framework, a Test Operations Partner, a Breeder Blanket System Partner and a Fusion Plant Controls Partner, alongside UKAEA’s separate LIBRTI tritium breeding programme.

For supply chain teams watching STEP, the near-term route in runs through the system-partner opportunities above and UKFE’s procurement portal, rather than a single Engineering Partner tender.

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