In the Guardian today:

The UK’s public spending watchdog has said it plans to investigate the Lower Thames Crossing, as campaigners voice concerns over the rising costs of one of the UK’s largest infrastructure projects.

The head of the National Audit Office (NAO) said he anticipated the agency would “examine and report” on the planned £11bn road tunnel between Kent and Essex, and that work to monitor the project had already started.

It emerged last month that £174m of additional public money was being made available for the scheme, which is estimated to cost more per mile than the HS2 high-speed rail link from London to Birmingham.

The government has committed £3.1bn to the construction of the twin 2.6-mile tunnel, which is designed to ease congestion on the Dartford Crossing, with the rest of the project expected to be financed by the private sector. ¹

No major UK Treasury-funded major capital project has been further from Scotland and further from its interests than this.

The LTC is an England-only road infrastructure project. It’s a new tunnel and linking roads between Kent and Essex, east of London managed by the UK Department for Transport. Total estimated costs have risen to around £10–11 billion or higher in some projections, with the government providing £3.1 billion upfront including recent additions like £891 million in the 2025 Budget and £174 million more to support planning, public works, and unlocking private finance for the rest.

If the private finance is not ‘unlocked, the UK Government would have to borrow the nearly £8bn difference. ²

How certain is it?

Not.

LTC’s own assessments highlight potential challenges in market appetite, legislation, toll levels. Private finance for roads is less common than for utilities/nuclear, which adds some uncertainty. ³

Will Scottish taxpayers pay a share?

Scottish taxpayers will contribute to the Lower Thames Crossing (LTC) project primarily through UK-wide taxation. This means Scottish taxpayers directly fund a share of the £3.1 billion potentially 300 million or more just as they do for other reserved UK-wide or England-delivered projects. If the private funding fails to be ‘unlocked’, it’ll cost Scots around £1bn.

Will we get it back via Barnett Consequentials?

In principle, increases in UK government spending on the LTC (classified under England-comparable transport budgets) should generate Barnett consequentials for Scotland, Wales, and Northern Ireland. This has happened for similar large English projects like aspects of HS2. ⁴

However, the Treasury decides case-by-case for specific projects whether spending is “comparable” or treated as UK-wide/national. For example there were no full consequentials for the 2012 Olympics. Critics and analysts such as the IFS⁵ noted disputes over projects like the 2012 Olympics and HS2. So it’s by no means guaranteed that Scotland will receive equivalent extra funding that fully offsets or matches.

Just these two?

No.

Kew Gardens and certain cultural/regeneration spending: Disagreements over comparability.

Various England-only prison, police, or local transport projects where classifications limited or excluded consequentials.

Targeted funding deals such as some City Deals or post-Brexit funds have sometimes bypassed Barnett entirely.

Broader Treasury decisions on capital projects such as certain London-centric infrastructure have been treated as non-comparable or UK-wide. 6

Clearly, here, with this project, as far as you can get from Scotland, Scots could be paying near £1bn for something that’s not of any meaningful benefit to Scotland.

Sources:

1. https://www.theguardian.com/uk-news/2026/jul/12/public-spending-watchdog-investigate-lower-thames-crossing-project
2. https://www.gov.uk/government/publications/department-for-transports-accounting-officer-assessment-summaries-for-the-government-major-projects-portfolio/lower-thames-crossing-ltc-accounting-officer-assessment-summary-february-2026
3. https://www.gov.uk/government/publications/department-for-transports-accounting-officer-assessment-summaries-for-the-government-major-projects-portfolio/lower-thames-crossing-ltc-accounting-officer-assessment-summary-february-2026
4. https://www.instituteforgovernment.org.uk/article/explainer/barnett-formula
5. https://ifs.org.uk/articles/barnett-formula
6. https://www.instituteforgovernment.org.uk/article/explainer/barnett-formula