HS2 "bat tunnel" costs broken down as claims price has gone up are dismissed

The Department for Transport (DfT) and HS2 Ltd have insisted the cost of HS2’s infamous bat mitigation structure remains around £95 million, as they broke down the costs for the work.

The DfT had been asked by the House of Commons’ Public Accounts Committee for a breakdown of costs for the structure at Sheephouse Wood, near Calvert in Buckinghamshire, amid reports the cost of the tunnel "may have risen significantly" since the last costing for it was provided in January.

In a letter dated June 20, the Department’s Interim Permanent Secretary, Jo Shanmugalingam, and HS2 Ltd Chief Executive, Mark Wild, said above-ground costs were circa £70m, with another £25m going on below-ground civil works to support the structure, echoing what the committee was told on January 31.

Using 2019 prices, the breakdown given in June's letter was:

• Design - £5.3m
• Preliminaries including management staff, temporary works, fuel, storage areas, site facilities and EKFB fee - £14.9m
• Concrete, reinforcement, formwork for substructure - £12.5m
• Concrete, reinforcement, formwork and ancillaries above ground – forming the base for the precast arches - £9.6m
• Waterproofing and ancillaries - £1.3m
• Manufacture and installation of arches, infill ventilation panels, including lightning protection and ancillary works - £49.7m
• Instrumentation and monitoring - £1.8m

Responding to suggestions the cost had increased, Shanmugalingam and Wild’s letter said: “We are aware of some media reports from March 2025 which speculated that the cost of the structure had risen significantly.

“It is our understanding that these reports reflect the same cost estimate but adjusted by the journalists themselves to account for inflation since 2019.”

Further media reports suggested the cost of the 900-metre-long tunnel had reached £125m, something an HS2 Ltd spokesperson dismissed, saying it "ignores the fact that work started on the tunnel years ago, meaning millions have already been spent and can't be inflated".

The DfT and HS2 Ltd were also asked for all costs to date relating to the tunnel.

The response said the total cost of the one kilometre stretch of HS2 at Sheephouse Wood (including the bat structure) is approximately £168m (at 2019 prices) but warned it would be “difficult to isolate costs incurred to a specific asset like the bat structure”.

The line near Calvert is one of the more expensive due to the boggy ground conditions in the area. This has led to deep foundations being laid.

Explaining this, the letter said: “Sub-contractors in the HS2 supply chain will typically be supplying materials and services which are deployed across the construction of the railway in this area.

“This means that their price and payment will span multiple activities – for example, hired plant equipment will be used across all elements of the works, not just on the bat structure.”

The cost of the structure was revealed by former HS2 Ltd Chair Sir Jon Thompson during the Railway Industry Association conference in London last year.

He told delegates HS2 Ltd had to obtain a licence from Natural England, which approved the bat mitigation structure, before asking planning permission from Buckinghamshire county council, he said.

“So when we go to [the] council and say: ‘Would you like to give us planning permission for this blot on the landscape that costs £100m’, of course, the answer to that is, you’ve got to be joking, right? Why would [they] like this eyesore?

“So now I’ve got two different bodies. One says I have to do it. The other one says: ‘No chance’. So what do you do? I reach for the lawyers and the environmental specialists and hydrologists and so on and so forth. It stretches out the time. I spend hundreds of thousands of pounds trying to do something, and then in the end, I win the planning commission by going over [the county council’s] head.”