By July 2025, National Grid Ventures stated that environmental and technical surveys for the Nautilus offshore hybrid interconnector would begin from autumn 2025. The surveys are intended to support detailed site assessments and inform the design of the project around the proposed Isle of Grain connection point in Kent. NGV indicated that survey activity would use both non-intrusive walkover methods and intrusive ground investigation techniques along the proposed converter station site, landfall location and route corridor.
On 1 December 2025, the European Commission adopted an updated Union list of Projects of Common Interest and Projects of Mutual Interest under Regulation (EU) 2022/869, in which Nautilus was classified as Project of Mutual Interest 4.5 within the Northern Seas Offshore Grids corridor. The list describes this project as a multi-purpose interconnector between Princess Elisabeth Island in Belgium and Kent in the United Kingdom, currently known as "Nautilus", confirming its status as a priority cross-border offshore electricity infrastructure link between Belgium and Great Britain.
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Nautilus is an Offshore Hybrid Asset (formerly described as a Multi‑Purpose Interconnector) being developed by National Grid Ventures in partnership with Belgian TSO Elia to provide a 1.4 GW HVDC subsea link between Belgium and Great Britain. The project is designed both as an interconnector for ...
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Multi-Purpose Interconnector (MPI), Offshore Hybrid Asset (OHA), NESO TEC PRO-000976
National Grid Ventures states on its Nautilus project page (updated July 2025) that environmental and technical surveys in the Isle of Grain area are expected to begin from autumn 2025, using non-intrusive and intrusive methods to inform site design. The projection is for survey mobilisation in autumn 2025 rather than a specific day, so 1 September 2025 is used as an approximate start-of-autumn marker.
By July 2025, Nautilus had progressed into a more advanced development stage and updated its UK grid connection proposal to the Isle of Grain in Kent. National Grid Ventures and its partners were working to further refine the converter station site, landfall location, and onshore route corridor, supported by ongoing environmental and technical site assessment activities.
On 10 June 2025, Elia Transmission Belgium confirmed it would not sign the previously negotiated HVDC converter contract for Princess Elisabeth Island, following a Belgian government decision to pursue an alternative concept for the energy hub's next phase at lower cost. The decision, driven by unprecedented global increases in HVDC infrastructure prices, formally ended the procurement process that had been suspended since February 2025. Belgian energy minister Mathieu Bihet gave Elia a mandate to develop an optimised configuration adapted to current market conditions, while reaffirming the strategic importance of both continued offshore wind development and a second interconnector with the UK. Elia CEO Frédéric Dunon confirmed discussions with UK partners would continue to find joint solutions for Nautilus. The Belgian government, CREG (energy regulator), FOD Economie, and UK authorities (Ofgem, NESO) will collaborate on the alternative concept. This requires an amendment to the ministerial decree on offshore grid design and a revision of the Federal Development Plan. Construction of the artificial island and HVAC connections for the first two wind farms (700 MW + 1,400 MW) continues on schedule, with the delay affecting only the HVDC-dependent third wind farm (1,400 MW) and the Nautilus interconnector. The overall project timeline is now expected to slip by approximately three years from the original 2032 target.
On 2 April 2025, Ofgem published its decision on the further detailed regime parameters for the Offshore Hybrid Asset pilot scheme, setting an adjusted form of the cap and floor regulatory regime for the two Pilot Non-Standard Interconnectors, including Nautilus. The decision confirms higher development risk and construction first-of-a-kind (FOAK) risk premia in the Interest During Construction (IDC) rate to reflect the novel risks of connecting to an offshore HVDC converter station, described as an energy island in the case of Nautilus. Ofgem explains that these parameters respond to developer feedback on risks such as complex multiparty interfaces, coordination with foreign TSOs and authorities, and untested offshore bidding zone market arrangements. Following this decision, the Pilot NSIs, including Nautilus, are expected to proceed with development towards the Final Project Assessment stage, subject to meeting their Initial Project Assessment conditions.
On 27 February 2025, National Grid Ventures confirmed that the grid connection agreement for the Nautilus interconnector at Leiston in Suffolk had been removed in coordination with the independent National Energy System Operator (NESO). This removal took Nautilus off the interconnector register and confirmed that the project would not be built in Suffolk nor would the Leiston connection agreement be used for any alternative project, with Nautilus instead proceeding towards connection at the Isle of Grain in Kent.
On 4 February 2025, Elia Transmission Belgium's Board of Directors decided to temporarily postpone signing HVDC converter contracts for Princess Elisabeth Island, directly delaying the Nautilus hybrid interconnector to the UK by approximately three years. Elia had been negotiating for two HVDC converters — one on the island and one on the Belgian coast — which are required both to connect the third Princess Elisabeth wind farm (1,400 MW) and to enable the Nautilus interconnector. The international tender revealed an overheated HVDC supply chain with significant price increases driven by scarcity of HVDC infrastructure, rising material costs, and inflation. Although the supplier's terms were comparable to those offered to other European grid operators, they were substantially higher than Elia's initial estimates. The chosen supplier had set a mid-February 2025 deadline to award the contract. Elia stated that making a unilateral decision without further political support in the current exceptional HVDC market conditions would be inappropriate, given that the cost increase would ultimately be borne by Belgian grid users. The postponement allowed the Belgian government more time to weigh the reference design (AC + DC infrastructure with Nautilus hybrid interconnector) against alternative concepts that had become more favourable under changed market conditions. Construction of the artificial island and HVAC contracts continued unaffected, securing 60% of the Princess Elisabeth wind zone.
On 12 November 2024, Ofgem approved the Initial Project Assessment for the Nautilus and LionLink electricity interconnectors. This regulatory decision confirmed the needs case for these new hybrid interconnector projects for British consumers, marking a major milestone in their development and enabling National Grid Ventures to continue progressing Nautilus towards subsequent design, permitting, and delivery stages.
On 12 November 2024, Ofgem published its decision 'Initial Project Assessment for the Offshore Hybrid Asset Pilot Projects', approving Nautilus to Belgium and LionLink to the Netherlands for a Pilot Offshore Hybrid Asset regulatory regime in principle. This follows its minded-to consultations and confirms the regulatory revenue framework (cap and floor) subject to conditions, securing the main revenue regime for Nautilus.
By October 2024, Elia confirmed that Nautilus was participating in Ofgem’s Window Three application period for the cap and floor regime as a Non-Standard Interconnector within the Offshore Hybrid Asset pilot scheme. This placed the 1.4 GW Belgium–Great Britain Offshore Hybrid Asset into the formal application process for a regulated revenue framework.
On 6 August 2024, National Grid Nautilus Limited notified the Gas and Electricity Markets Authority (Ofgem) that it had submitted an application for an electricity interconnector licence for the Nautilus project, and Ofgem published a notice inviting comments on the licence application up to 13 September 2024.
On 15 July 2024, Ofgem published the consultation 'Consultation on changes to the Initial Project Assessment of the Nautilus Offshore Hybrid Asset', presenting updated IPA analysis for Nautilus after changes to its GB connection location and Belgian energy island configuration and inviting stakeholder responses by August 2024.
On 31 May 2024, in their joint response to Ofgem’s consultation on the Initial Project Assessment for Offshore Hybrid Assets, National Grid Ventures and Elia confirmed a project decision to move Nautilus’s GB connection point from Grain in Kent to the new Friston substation at Leiston in Suffolk. They stated that, based on ESO analysis and independent constraint‑cost modelling by Afry, connecting at Leiston would materially reduce constraint costs for GB consumers compared with Grain, and committed to progress a corresponding change of connection location through the licensing process.
On 1 March 2024, Ofgem published the consultation document 'Initial Project Assessment of the Offshore Hybrid Asset Pilot Projects', setting out its minded-to positions for the Nautilus and LionLink projects under the OHA pilot scheme and inviting stakeholder responses by 30 April 2024.
On 15 December 2022, Ofgem issued its 'Decision on Multi-Purpose Interconnector pilot project selection' letter confirming that the Nautilus project to Belgium and the Eurolink project to the Netherlands had been selected as pilot projects to proceed to the Initial Project Assessment stage under the MPI/OHA scheme, having passed eligibility checks including a GB connection agreement by end-2032.
In 2021, National Grid Ventures conducted a non-statutory public consultation on the early Nautilus Offshore Hybrid Asset proposals. The consultation was supported by materials such as a September 2021 briefing pack, community consultation leaflet, information sheets, maps, and an October 2021 non-statutory consultation feedback form. A feedback summary document is also provided on the project website. These materials are now archived as part of the "previous consultation" and no longer reflect the current Nautilus proposals.
Nautilus project materials from National Grid Ventures and National Grid ESO describe that ESO completed an appraisal of Nautilus’s grid connection request and identified the Leiston / Sizewell area in East Suffolk as the preferred connection zone. By 2020–2021, National Grid documentation refers to Nautilus already having a connection agreement in the Leiston area, which indicates that the ESO appraisal and offer acceptance were concluded earlier. Considering the CEF 2019 PCI action for Nautilus early‑stage development and the presence of an agreed connection location by 2020–2021, it is reasonable to place the ESO grid offer appraisal and acceptance around 2019.
National Grid Ventures’ Nautilus project documentation indicates that NGV applied to National Grid Electricity System Operator (ESO) for a grid connection point in the Leiston / Sizewell area in East Suffolk during the early development phase. The 2021 National Grid Nautilus project update and associated written responses to the East Anglia One North and Two examinations describe Nautilus as already holding a connection agreement with ESO by 2020–2021. This implies the underlying grid connection application was made and processed several years earlier, during the 2010s. Given the CEF 2019 PCI action for Nautilus early-stage development and the status of the connection agreement by 2020, the grid application can be reasonably dated to around 2019.
In March 2019, National Grid Ventures (NGV) submitted a request to the Secretary of State for Business, Energy and Industrial Strategy under Section 35 of the Planning Act 2008 for the proposed Nautilus Interconnector to be treated as a Nationally Significant Infrastructure Project requiring a Development Consent Order. This Section 35 process establishes the Secretary of State as the final decision-maker for Nautilus and places the project within the DCO consenting regime, which in turn requires NGV to undertake a thorough Environmental Impact Assessment and consultation process before submitting any application.
National Grid Ventures (NGV) and Belgian transmission system operator Elia established a joint venture to develop the Nautilus project, a 1.4 GW Offshore Hybrid Asset interconnector linking Great Britain with Belgium via the Princess Elisabeth Island and associated offshore wind connections.
National Grid Ventures indicates that, once consents are granted and a Final Investment Decision is taken for the Nautilus Interconnector, construction will commence. This construction phase will cover the onshore and offshore infrastructure required for the 1.4 GW multi-purpose interconnector between East Suffolk in Great Britain and Belgium, including converter stations and subsea and onshore cable systems.
National Grid Ventures indicates that, following the granting of consent and a planned Final Investment Decision for Nautilus, construction of the interconnector will commence. This construction phase will cover installation of onshore and offshore infrastructure, including underground cabling works and associated assets in East Suffolk and the subsea HVDC link between Great Britain and Belgium.
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