• building approximately 18 km of new 400 kV overhead line
• building approximately 11 km of new 400 kV underground cable
• removing around 27 km of existing 132 kV and 400kV overhead line between Burstall Bridge and Twinstead Tee
• additional works to support construction, including temporary construction compounds, site offices, haul roads and new road junctions (bellmouths)
• works to deliver a minimum of 10% biodiversity net gain, including planting and other environmental enhancements.

We are also building a new substation at Twinstead Green (between Butler's Wood and Walegrave Wood). The substation is where National Grid's high voltage transmission network connects into the low voltage network run by UK Power Networks, who is the distribution network operator in this area. We applied to build the GSP substation through a separate planning application to Braintree District Council, as this will reduce the overall amount of time it will take to build the project.

You can view the detailed plans included in our application for development consent by visiting the Planning Inspectorate's website here.

Current and upcoming works

Across the first half of 2026, we have been carrying out vegetation clearance and creating new bellmouths (road junctions) so that we can build temporary haul roads for construction vehicles to use. Throughout May, you may notice increased activity as Balfour Beatty, who are carrying out construction work on National Grid’s behalf, continue with vegetation clearance and the coppicing of trees. We will also need to implement a series of short-term traffic management measures (such as temporary traffic lights or short interruptions to the flow of traffic) at points along the route of our project so that we can carry out this work safely.

Before we carry out any vegetation clearance or coppicing, we consider the maturity and condition of any vegetation our works would impact. We then seek the approval of your local district council in line with the conditions of our development consent order. As part of this, if works could impact mature, veteran or high-value trees and hedgerows, we will seek to carry out coppicing work rather than outright removal where possible. Should works require any temporary traffic management so that it can be carried out safely, then we will also request a permit from your county council in order to do this.

Works will only be carried out once the appropriate permissions are in place. They will be paused if nesting birds are identified and will only continue once the nest is no longer active. Any planting we remove will be reinstated at the end of the construction of our project in line with Reinstatement Planting Plans, which we will agree with your local council.

Full details of where we expect to implement traffic management measures can be found in the table below. These dates are subject to change, so we will update this page regularly as the works progress.

Oak Road update 

The planned road closure and diversion which we had planned on Oak Road from 11 May to 8 June 2026 will not go ahead as planned. 

We need to complete some preparatory work before the traffic management can start, and this work has not finished yet. We now expect the works to take place on new dates in June. 

We'll share the confirmed dates, timings and diversion route as soon as we can, and notify the area via postcards as we did originally. 

Surveys

If a survey cannot take place on the scheduled date (due to factors such as poor weather conditions), we will endeavour to reschedule the survey in a timely manner.

Access to land plots is agreed before any surveys take place. If you are a landowner and have questions about surveys on your land, please get in touch via your usual point of contact or the details at the bottom of the page.

Completed works

In 2025, we carried out work to build our main construction compound off the A134, between Leavenheath and Asssington. The main construction compound is being used for site offices and for the delivery and storage of materials. The compound will be removed and the site will be restored to a condition suitable for return to its original use once construction is complete. 

At the site of our new substation, we have built a new 132 kV pylon for UK Power Networks and a temporary 400 kV pylon so that further construction activity can take place. We have also started to install electrical equipment.