Grid First, Campus Second: How Laing O’Rourke Reached the AI Boom Through a Tunnel in St John’s Wood

The AI boom has a familiar face: a giant shed full of servers on the edge of a town, promising thousands of jobs and a very large power bill. What that picture leaves out is the reason so many of those sheds sit half-built or unstarted. You can have the land, the funding and the chips and still not be able to switch the thing on, because the grid connection is not there.

In Britain that constraint is acute. The queue of projects waiting to connect around London runs into hundreds of gigawatts, and years of waiting have become normal. So the work that has to happen first, and gets funded first, is the transmission upgrade that creates the capacity. National Grid’s North West London Upgrade is exactly that kind of job, and in mid-August it moved from plan to awarded packages.

For anyone deciding where to point a business development team, the read is simple. The most bankable data centre-adjacent work in the country right now runs through substations, cables and a tunnel in St John’s Wood, and the names on the contracts tell you who is positioned to win it.

The work that actually reaches the AI boom

Why the bankable job is the connection, not the data hall

The data hall is the visible prize, but power is the binding constraint. Across large parts of the UK, and around London in particular, a data centre cannot connect for years, which is why developers chase sites with existing grid rights and why the government keeps consulting on how to clear the queue. That mismatch flips the usual order of who gets paid first. Before a server ever hums, someone builds the substations, pulls the cables and reinforces the lines that make the connection real.

National Grid’s North West London Upgrade is that enabling work at scale. It reinforces the transmission network from Bedfordshire through Hertfordshire into North West London, creating the headroom to connect five new data centres with a combined demand of 1GW. The official cost was redacted from National Grid’s public submission, though trade press has consistently put it around £1 billion. Either way, the programme does not build a single data centre. It decides whether five of them can exist.

That is the WIIFM for a UK contractor. The AI story most likely to convert into signed, funded, multi-year workload runs through grid infrastructure, and it is being awarded now.

What Laing O’Rourke and HMJV actually won

Substations, 400kV cables and a tunnel that was built ready

The scope splits cleanly. Laing O’Rourke has been appointed to deliver new and upgraded substations at Letchmore Heath, Elstree and St John’s Wood. The Hochtief Murphy joint venture, HMJV, will install new 400kV cables and upgrade the existing transmission tunnel between Elstree and St John’s Wood. Hyundai Electric supplies the transformers and other major electrical equipment, and Siemens Energy provides the shunt reactors at Elstree.

The route runs from Sundon in Bedfordshire to Elstree in Hertfordshire and on to St John’s Wood in London. It includes upgrades at Sundon, a 35km reconductoring programme on the Sundon to Elstree line, an extension to Elstree substation, a new substation at Letchmore Heath and reinforcement at St John’s Wood. More than 200km of overhead line will be upgraded, and another 60km of new high-voltage cable is pulled through the existing Elstree to St John’s Wood tunnel.

The tunnel is the detail worth noticing. It stretches more than 20km, already carries transmission cables, and was designed in the early 2000s with room for an extra circuit. That foresight lets National Grid add a 400kV route without digging a new tunnel under London, the kind of buried, unglamorous capacity that makes a programme like this deliverable.

Why these two firms, and what it signals

The work is going to contractors already inside the grid

This did not land with a firm that woke up interested in transmission. Laing O’Rourke was appointed construction partner to National Grid’s Great Grid Upgrade in 2024, and has delivered the Letchmore Heath substation since March 2025. Bolting the new substation packages onto that scheme brings efficiencies across design, construction and commissioning, which is why an incumbent tends to keep winning.

The signal for the rest of the market is clear. High-voltage substation work, 400kV cabling and deep-tunnel upgrades sit behind framework positions and a track record National Grid already trusts. If your firm holds those, the AI boom arrives as a headline contract. If not, the same boom still reaches you, but as subcontract and supply packages hanging off someone else’s programme. Knowing which side of that line you are on is the difference between chasing the work and being invited to it.

The pipeline behind the headline

Connections reform is turning a queue into a schedule

Part of why grid enabling works now carry real workload visibility is a quieter change in how projects connect. Connections reform, approved by Ofgem in April 2025, replaced the old first come, first served queue with a deliverable pipeline that prioritises projects that are ready and needed. The old queue had swollen to several times the capacity Britain actually needs, clogged with schemes that were never going to be built.

The clean-up is well underway. By June 2026, NESO and the network operators had issued connection offers to more than 700 shovel-ready projects, around 58% of the pipeline needed before 2030, roughly 37GW of capacity, with the rest of the 2030 offers due by early 2027. For a contractor, a filtered pipeline is what turns speculative interest into schedulable work, and it gives programmes like the North West London Upgrade a credible run of years behind them.

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