Parliament's spending watchdog, the Public Accounts Committee (PAC), has concluded that a "catastrophic" decision by the Ministry of Justice (MoJ) to sign a 10-year lease on HMP Dartmoor, a prison with dangerously high levels of radon gas, is expected to cost UK taxpayers more than £100 million. The committee branded the affair "an absolute disgrace," rejecting the MoJ's defense that the deal was driven by an urgent need for prison places.

The agreement to rent HMP Dartmoor from the Duchy of Cornwall, the private estate that provides income for Prince William, was signed in 2022 by senior civil servants from HM Prison and Probation Service (HMPPS). The PAC criticized this as a decision made "in a blind panic" to guarantee prison places. The Category C prison, which held many sex offenders, was ultimately closed in August 2024 after levels of radon, a colorless and odorless radioactive gas that causes approximately 1,100 lung cancer deaths annually in the UK, were detected up to 10 times higher than recommended limits in some areas. The government admitted awareness of "elevated readings" of the gas at Dartmoor as early as 2020, with reports also indicating detection of higher-than-recommended levels in 2007.

Despite the prison's clear unsuitability due to radon contamination, the contract, which commenced on Christmas Day 2023, contains terms preventing its termination until at least December 2033, when the first break clause can be exercised. Consequently, HMPPS is currently paying around £4 million per year for the unusable prison, covering rent (which includes an annual £1.5 million), business rates, and security costs. Furthermore, the government is committed to paying an additional £68 million for "fabric improvements" to the Dartmoor site over the period of the lease. This brings the total projected cost to the taxpayer to more than £104 million from the prison's closure in August 2024 until the earliest possible break in the contract. The PAC harshly criticized HMPPS for failing to negotiate a better deal or safeguards, despite their prior knowledge of radon's presence at the site.

Sir Geoffrey Clifton-Brown, the Conservative chair of the Commons' cross-party Public Accounts Committee, vehemently stated that the MoJ's handling of HMP Dartmoor was "an absolute disgrace, from top to bottom." He firmly rejected the MoJ's explanation of a prison capacity crisis, asserting that Dartmoor appeared to the committee to be a "perfect example of a department reaching for a solution, any solution, in a blind panic and under pressure." The committee's report urged the government to learn from this "catastrophic failure" and ensure nothing similar occurs again. Jo Farrar, the MoJ’s permanent secretary, defended the 2022 decision before MPs in October, explaining that the prison system was "at risk of running out of prison places" at the time, and Dartmoor provided over 600 essential spaces. A Ministry of Justice spokesperson reiterated this, citing a "crisis in our prisons system" inherited by the current government.

The decision to close the jail, forcing the relocation of 682 inmates and 159 staff, followed years of monitoring and attempts to mitigate the radon levels, with staff having begun monitoring as early as 2010. Questions have since been raised about whether HMPPS could have acted sooner to address the risks. Significantly, more than 500 former inmates and prison officers are now pursuing legal claims against the government, alleging that their health was jeopardized. An investigation into radon levels at the prison launched by the Health and Safety Executive (HSE) in 2023 is currently ongoing.

The future of HMP Dartmoor, one of Britain's oldest jails opened in 1809, remains uncertain, as the MoJ and HMPPS currently lack clear plans for its potential reopening. They are awaiting the outcome of the HSE's review of current workplace regulations on radon before assessing the necessary works and making a decision based on the best value for money for taxpayers. Mark Fairhurst, the national chair of the Prison Officers Association, welcomed the PAC's report, describing it as "abhorrent that such a failure has not yielded consequences for the high-ranking decision makers that not only put everyone within Dartmoor prison at risk but also wasted millions of pounds of tax revenue."