IN Brief:
- National Grid proposes approximately 60km of new 400kV overhead line between Lincolnshire and Leicestershire.
- Two new substations are planned near Corby Glen and Wartnaby, alongside around 66km of existing-line upgrades.
- Stage 2 consultation runs until 3 November ahead of further refinement and a Development Consent Order application.
National Grid has opened a second-stage consultation on refined plans for the Weston Marsh to East Leicestershire reinforcement, a 400kV transmission project spanning Lincolnshire, Leicestershire, and Northamptonshire.
The revised scheme would create approximately 60km of new overhead line between Weston Marsh in Lincolnshire and the Wartnaby area of Leicestershire, supported by two new substations near Corby Glen and Wartnaby. National Grid also proposes around 66km of upgrades to the existing overhead network between the new Wartnaby substation and Grendon Substation in Northamptonshire.
The project forms part of the Great Grid Upgrade and has been identified by the National Energy System Operator as reinforcement required for future electricity needs. National Grid says the existing network does not have sufficient capacity to transport the volumes of electricity expected as generation changes and demand grows through electrification of transport, heating, and industry.
Consultation runs from 8 September to 3 November 2026. The latest design follows a first-stage consultation in summer 2025, with National Grid using community feedback, technical work, and environmental assessment to refine the route before preparing its Development Consent Order application.
At the northern end, the new circuit would begin at Weston Marsh B, a substation proposed separately as part of the Grimsby to Walpole project. The route would then run south-west through Lincolnshire to the proposed WMEL-A substation near Corby Glen before continuing to WMEL-B near Wartnaby.
National Grid’s detailed proposals specify new 400kV overhead line supported by steel lattice pylons. South of Wartnaby, the project would upgrade existing 400kV infrastructure towards Grendon rather than create a wholly new corridor, allowing the reinforcement to increase transfer capability across both new and existing assets.
The electrical requirement is simple to describe but less straightforward to deliver. New generation only contributes fully if the transmission system has enough thermal capacity, voltage support, and operational margin to move its output towards demand. Where circuits are heavily loaded, additional generation or demand can increase constraint costs or limit the connections that can operate simultaneously.
A reinforcement of this scale therefore combines several engineering disciplines. New overhead circuits require towers, conductors, insulators, foundations, earthing, access, and environmental mitigation, while the substations must provide switching, protection, control, metering, auxiliary supplies, and interfaces with both new and existing circuits.
The existing-line upgrades are equally significant because network capacity is determined by the most restrictive elements along a power-flow path. Increasing capacity on a new 400kV section would have limited value if adjoining circuits remained unable to transfer the additional power, making uprating work part of the same system problem rather than an optional add-on.
Construction also has to be sequenced around an operating transmission network. Existing circuits may require planned outages for conductor replacement, protection changes, and commissioning, while new substations have to be energised and tested without undermining security of supply on neighbouring routes.
Planning adds another constraint. Route refinement has to balance electrical performance and constructability with land access, environmental effects, local impacts, and the practicalities of maintaining assets over several decades. Consultation responses can therefore alter alignment and mitigation even where the underlying system need remains unchanged.
National Grid says the government’s community-benefit framework would make £200,000 available per kilometre of new overhead line and £530,000 per new substation for eligible communities. Those payments sit alongside the statutory planning process rather than replacing it, but they add another delivery consideration across a project extending through several local authority areas.
The programme also illustrates the difference between generation targets and grid readiness. Solar, wind, storage, and other low-carbon assets can often be developed on shorter schedules than major transmission infrastructure, which must pass through route design, environmental assessment, consenting, land agreements, equipment procurement, construction, and commissioning.
That timing mismatch is pushing several large British transmission projects forward in parallel, increasing demand for conductors, transformers, switchgear, protection equipment, specialist contractors, and engineering staff. Procurement and outage planning will therefore matter alongside planning consent if the reinforcement is to arrive when forecast power flows require it.
For Weston Marsh to East Leicestershire, the immediate milestone is the consultation close on 3 November. National Grid must then assess responses and continue refining the scheme before its consent application, while the engineering case remains centred on creating a stronger 400kV path through the East Midlands before today’s transfer limitations become a more expensive operational constraint.
