Laing O’Rourke and the Hochtief Murphy joint venture (HMJV) have secured major construction packages on National Grid’s £1 billion North West London Upgrade, a substantial infrastructure programme designed to strengthen electricity capacity and support the rapid expansion of data centres and digital infrastructure.
The project will reinforce the electricity transmission network running between Bedfordshire, Hertfordshire and North West London, creating additional capacity to connect five new data centres with a combined electricity demand of 1GW.
Laing O’Rourke has been appointed to deliver new and upgraded substations at Letchmore Heath, Elstree and St John’s Wood, forming a major element of the programme’s civil engineering and electrical infrastructure works.
HMJV will undertake the installation of new 400kV cables and upgrade the existing transmission tunnel between Elstree and St John’s Wood.
The wider supply chain will include Hyundai Electric, which will provide transformers and other major electrical equipment, while Siemens Energy will supply shunt reactors for the upgraded Elstree substation.
Stretching from Sundon substation in Bedfordshire through Elstree in Hertfordshire and onwards to St John’s Wood in London, the programme represents a significant reinforcement of the electricity infrastructure serving the capital and surrounding areas.
The works include upgrades at Sundon and a 35km reconductoring programme on the Sundon-to-Elstree overhead line. Elstree substation will be extended, a new substation will be constructed at Letchmore Heath and further reinforcement works will be undertaken at St John’s Wood.
More than 200km of overhead line will be upgraded as part of the programme, while another 60km of new high-voltage cable will be installed through the existing 20km-long transmission tunnel between Elstree and St John’s Wood.
The tunnel was originally designed with sufficient capacity to accommodate an additional transmission circuit, enabling National Grid to significantly increase capacity while making use of existing underground infrastructure.
The investment comes as the growth of artificial intelligence, cloud computing and other digital services drives increasing demand for energy-intensive data centre developments, particularly around London and the wider South East.
The ability to secure sufficient electricity connections has become an increasingly important consideration for the development and construction of new data centre campuses. National Grid’s programme will provide capacity for five new facilities while simultaneously strengthening the network for homes, businesses and future developments.
National Grid said the investment will improve network resilience, unlock future electricity connections and reduce long-term constraint costs across the transmission system.
The North West London Upgrade brings together major civil engineering, tunnelling, cabling, substation and electrical engineering packages within a single infrastructure programme. With Laing O’Rourke and HMJV taking leading delivery roles, the £1 billion investment will provide critical new capacity as London’s built environment responds to the continued expansion of AI and digital infrastructure.
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