This article covers the story behind the Sheephouse Wood structure commonly referred to as the HS2 bat tunnel or HS2 bat shed. We will cover where it is located, how its costs escalated from £40m to £216m, who is building it, and why it matters for anyone working in UK infrastructure procurement.
The structure runs alongside Sheephouse Wood, a 56-hectare Site of Special Scientific Interest (SSSI) between Bicester and Aylesbury. Sheephouse Wood is part of the wider Bernwood Forest landscape and home to 13 bat species.
The wood hosts the most northerly known breeding population of Bechstein's bat in Europe, estimated at around 300 individuals. The railway corridor here is partially disused and dates back to the 19th century.
HS2 selected this route in the early 2010s, balancing journey time, cost, and engineering feasibility.
In the below Google maps custom map, you can see the exact location of the Bat tunnel.
For an interactive view of the entire HS2 route including this location, see our HS2 Route Map.
HS2's route through the Calvert corridor was chosen during detailed planning in the late 2000s. The route cuts through Sheephouse Wood, where species are protected under the Wildlife and Countryside Act 1981 and the Conservation of Habitats and Species Regulations 2017.
Natural England's position on the Bechstein's bat colony was clear: no bat death is acceptable. However, HS2 Ltd proposed the structure as mitigation. Natural England did not require it, did not advise on its design, and did not influence its costs. The Bat Conservation Trust has stated it had no involvement and that the bat tunnel was "a consequence of poor decisions made by HS2 Ltd and approved by parliament."
HS2 Ltd examined 17 potential mitigations before concluding the 1km enclosure was the only option that met the three-part legal test for European Protected Species licences:
Parliament approved the mitigation through the High Speed Rail (London to West Midlands) Act 2017. Then the scope changed. The structure had to accommodate not just two HS2 tracks but also two East West Rail lines, doubling the width.
HS2 then needed separate planning permission from Buckinghamshire Council, which refused. Four years of engagement followed before a Planning Inspector overrode the refusal in February 2024.
The cost has escalated significantly. The original budget when procurement started was approximately £40m. By 2019, a Freedom of Information request revealed HS2 Ltd estimated £95m at 2019 prices.
In November 2024, Sir Jon Thompson confirmed the cost had passed £100m. By March 2025, New Civil Engineer reported £119m adjusted for inflation. Then in June 2025, a Department for Transport (DfT) letter to the Public Accounts Committee revealed the full picture: the entire 1km section of railway at Sheephouse Wood costs £168m at 2019 prices, approximately £216m adjusted for inflation.
The bat structure itself accounts for roughly 37% of the section costs. The remainder covers EKFB contractor costs including design, risk, fees, and direct works.
What drove the cost so high? Poor ground conditions due to an adjacent landfill. The 120-year design life with minimal maintenance allowance. Passive ventilation and fire resistance requirements. Capacity for up to 36 high-speed trains per hour. The structure also had to withstand multiple concurrent train derailment scenarios.
You might have seen the "cost per bat" calculation floating around. At £100m and a colony of 300 Bechstein's bats, that works out to approximately £333,000 per bat. Ecologists have challenged this framing as misleading. The structure protects the entire Bernwood Forest ecosystem, including 13 bat species, rare invertebrates, and legally protected breeding birds, over 120 years. It is not protecting 300 individual animals at a single point in time.
HS2 Ltd is the government-owned company responsible for delivering the project. The bat tunnel sits within the EKFB joint venture's delivery package, Contract Lots C2 and C3, awarded at a combined value of £2.3bn.
EKFB comprises Eiffage, Kier, Ferrovial Construction, and BAM Nuttall. Their scope covers an 80km section from the Chiltern Tunnel north portal to Long Itchington Wood, including 15 viaducts, 6.9km of green tunnels, 81 bridges, and 30 million cubic metres of excavation.
The procurement chain extends deep into the supply chain. On Stotles, you can see specific contracts flowing through EKFB's delivery package, including the EKFB JV Bat Acoustic Deterrent tender. Even bat deterrent equipment operating at 20-100kHz goes through formal competitive tendering.
HS2's supply chain is structured in tiers. Tier 1 is HS2 Ltd. Tier 2 includes the main works joint ventures like EKFB. Tier 3 and below includes specialist subcontractors, labour suppliers, and material providers. Over 8,000 consents were required across the Phase 1 route from public bodies, each creating procurement activity at every level.
A quick look at Stotles' publicly facing platform shows the EKFB JV buyer profile with subcontracting activity on the bat tunnel's section of the route.
In early 2025, HS2 launched an investigation following whistleblower allegations that Danny Sullivan Group was overinflating rates. The company allegedly charged Construction Industry Scheme (CIS) self-employed workers out at PAYE rates on the West Midlands section of the project.
Balfour Beatty terminated all contracts with Danny Sullivan Group in July 2025 after finding the company had misinformed it about worker classification. BAM, part of the EKFB joint venture, then terminated Danny Sullivan Group's involvement on the bat tunnel specifically. Around 30 to 40 workers were transferred to other employers.
HMRC was formally referred. Danny Sullivan Group denied deliberate wrongdoing but acknowledged "erroneous engagement" of CIS workforce operatives. Sir Geoffrey Clifton-Brown MP, chair of the Public Accounts Committee (PAC), called HS2 "a cautionary tale that should be studied by future governments in how not to run a major project."
Sir Jon Thompson, HS2's chairman, called it a "bat shed" at the Railway Industry Association conference in November 2024. The formal name is the Sheephouse Wood Bat Mitigation Structure. Moxon Architects designed it as part of the ASC (Arcadis Setec COWI) design team working for the EKFB joint venture.
Each arch spans approximately 23 metres wide and rises up to 10 metres high. The structure accommodates two HS2 lines and two East West Rail lines, with a 120-year design life and minimal maintenance requirements.
The bat tunnel has become the poster child for UK planning reform. It was referenced at least ten times during the Planning and Infrastructure Bill's second reading.
Rachel Reeves described it as evidence that environmental requirements make infrastructure "far too expensive and far too slow." Steve Reed called it an "absurd expense." The PAC called HS2 a "casebook example of how not to run a major project."
The counter-narrative is equally forceful. The Bat Conservation Trust says the bat tunnel is being used to "scapegoat bats and weaken environmental protections without solving the real causes of planning delays." Bob Stebbings, the ecologist who campaigned for bat legal protection in the 1980s, has publicly stated that the bat tunnel "was never recommended by bat advisors but was decided by HS2 planners."
Transport Secretary Heidi Alexander stated in July 2025 that HS2 expenditure to date had reached £40.5bn at nominal prices. She was "not in a position to say with confidence how much HS2 will cost or when it will be delivered."
Protected species surveys, mitigation design, and licensing are standard requirements for UK infrastructure contracts. The bat tunnel is not unique to HS2, though its scale and cost are exceptional.
Suppliers weighing their bid/no-bid decision on HS2 packages or similar major projects factor environmental compliance into programme and cost estimates. The bat tunnel is not HS2's only bat mitigation. Other structures and habitat creation schemes exist along the route for multiple protected species including great crested newts, badgers, and dormice.
Key compliance considerations for suppliers:
A project approaching £80bn in total estimated cost involves tradeoffs between environmental protection, engineering complexity, and public money. When a 1km bat structure escalates from £40m to a section cost of £216m, the public deserves to understand why. When a labour supplier is terminated over allegations of inflated rates, the procurement chain that allowed it deserves scrutiny.
This Stotles guest pass for High Speed Two (HS2) Ltd gives you a preview of the full HS2 profile complete with 181 notices, 558 connected suppliers, upcoming contract expiries, and the complete procurement history in one view.
