HS2 is now expected to cost between 87.7 billion and 102.7 billion pounds, the line will carry trains slower than first promised, and the first services from Old Oak Common to Birmingham will not run until somewhere between 2036 and 2039. Roughly 43.6 billion has already been spent. The painful bit for anyone who builds things: most of the overrun was not bad luck. It was scope that got missed, estimates that were too low, and delivery that ran slow. If you run projects, that should feel uncomfortably familiar.
On 19 May 2026, the Transport Secretary stood up in the Commons and gave HS2 yet another reset. The new completion estimate sits between 87.7 billion and 102.7 billion pounds in today’s money. Trains will run at 320 km/h instead of the 360 km/h originally pitched. And the opening date for the first stretch has drifted into the back half of the 2030s.
We pulled this one apart on the latest Bricks & Bytes episode because, honestly, the numbers are almost funny until you remember who pays. This is taxpayer money, and the gap between what was promised and what is being delivered is the kind of thing that ends careers in private construction. So what actually went wrong, and what does it tell the rest of us about running big builds?
Here is the thing worth sitting with before we get into the detail. HS2 is not a story about one bad decision. It is a story about a hundred small ones, compounded over fifteen years, with nobody able to produce a cost estimate anyone could trust. That is a project management problem, not a politics problem. And it is one every reader of this newsletter has lived through on a smaller scale.
The headline number keeps moving, and that is the real problem
How a £15bn idea became a £100bn project
When HS2 was first tabled back in 2010, the price tag sat between 15.8 billion and 17.4 billion pounds. The last government later worked to a budget range of roughly 35 to 45 billion in 2019 prices. The new estimate, converted to that same 2019 base, is about double that. So depending on which starting line you pick, the cost has gone up several times over.
What makes this worse than a normal overrun is that nobody seemed able to say what the true number was at any given point. The Stewart review found that budget control was undermined by HS2 Ltd’s repeated inability to produce reliable cost and schedule estimates. When you cannot measure where you are, you cannot tell anyone where you are going. The estimate moves because the ground under it was never solid.
For a construction exec, that is the lesson hiding in plain sight. The cost did not balloon on the day of the announcement. It ballooned quietly, over years, while the official figure stayed comfortable and wrong. Bad news that travels slowly is still bad news. It just costs more by the time it arrives.
- Two-thirds: scope, estimates, delivery. Works missed from the original plan, under-estimation, and inefficient delivery. All of it inside the control of HS2 Ltd, its suppliers, and previous governments.
- One-third: inflation. Real, but the part that was hardest to avoid. Inflation was not factored into earlier estimates regularly enough.
- The kicker. Cancelling now would cost roughly as much as finishing, while delivering none of the benefits. So the project limps on.
Why does Britain build rail so expensively?
The planning maze, the tunnels, and the price of saying yes to everyone
HS2 has the unhappy distinction of being one of the most expensive high-speed rail lines in the world per kilometer. Analysts at Britain Remade have estimated it runs many times more expensive than France’s Tours-to-Bordeaux line. Even on its 2013 budget, before the worst of the overruns, one analysis pegged it at around 3.7 times the French cost per mile. Spain has built thousands of miles of high-speed track over the years for a fraction of what HS2’s far shorter route is costing.
Why the gap? A big chunk comes down to how the UK gets projects approved and built. One contractor involved in HS2 put the blame on the permit and environmental study process, pointing out that in Spain the government secures consents and environmental permits first, then hands a clean project to the contractor to deliver. In the UK, much of that risk and cost lands inside the build itself. Add a route packed with tunnels to keep communities onside, the famous 100 million pound bat protection structure, and a scrapped Euston redesign, and the meter just keeps running.
None of this is unique to rail. Anyone bidding work in the UK knows the feeling: the cost of saying yes to every objection, every late change, every consent that arrives after you have already mobilized. HS2 is that dynamic at national scale, with the brakes off.
You couldn’t mess it up more if you tried. Half the stations, slower trains, opening 13 years late, and the bill has tripled. The maddening part is that none of it was a surprise to the people on the ground.The Bricks & Bytes panel, on the HS2 reset
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The pipeline, the playbook, and the trap of starting before you are ready
If you build, invest, or sell into UK construction, HS2 matters beyond the comedy of the headline. A megaproject of this size is a pipeline. It keeps tunnelling crews, fabricators, and specialist subcontractors busy for years, which is exactly why the government concluded that cancelling would cause bigger problems down the line than finishing. Kill the project and you kill a chunk of the work that lets the sector keep skilled people employed between jobs.
There is also a hard operational lesson here, and it echoes something we hear from the smartest founders and GCs on the show. Big projects go wrong when they start before all the ducks are in a row. Land not fully secured, scope not fully defined, contracts signed against advice. You bet on figuring it out later, and later always costs more. The fix is boring and it works: nail the estimate, secure the consents, define the scope, then build. Slower at the start, far cheaper at the end.
For the ConTech crowd, HS2 is also a flashing sign about data. The reason nobody could trust the numbers is that the numbers were never properly captured or categorized in the first place. That is precisely the gap a wave of construction software is now trying to close, turning messy project history into estimates people can actually rely on. The appetite for tools that make cost and schedule defensible has rarely been higher.
The government’s latest estimate, given on 19 May 2026, is a range of 87.7 billion to 102.7 billion pounds in 2025 prices. That is roughly double the 35 to 45 billion (2019 prices) the previous government worked to, and many times the original 2010 figure of around 15.8 to 17.4 billion. About 43.6 billion had already been spent by the end of February 2026. (Source)
Roughly two-thirds of the increase is down to works missed from the original scope, under-estimation, and inefficient delivery – all within the control of HS2 Ltd, its suppliers, and previous governments. The remaining third is inflation that was not factored into earlier estimates often enough. (Source)
The first services between Old Oak Common and Birmingham Curzon Street are now estimated to start between May 2036 and October 2039. Trains will not reach central London at Euston until somewhere between May 2040 and December 2043. The original plan had the line opening in 2026. (Source)
HS2 is one of the most expensive high-speed lines in the world per kilometer. Analysts point to the UK’s planning and environmental consent process, which loads risk and cost onto the build itself, plus a tunnel-heavy route and design changes made to reduce opposition. In Spain, the government secures consents up front and hands contractors a cleaner project to deliver. (Source)
According to the government, cancelling would cost roughly as much as completing the line while delivering none of the transport benefits. Internal reviews put decommissioning costs high enough that finishing was judged the more practical option, even at the new price. (Source)
Institution of Civil Engineers: What went wrong on HS2
New Civil Engineer: HS2 cost estimated to exceed £100bn
PBC Today: HS2 cost estimate reaches £102.7bn
Britain Remade: Why HS2 costs more than France
Department for Transport via Specification Online: HS2 delivery update
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