We conducted a pilot randomised controlled trial (the PHaCT study), including a process evaluation to assess the acceptability of a housing-led Critical Time Intervention (CTI) for prison leavers and the use of a trial design. This paper presents the process evaluation findings.

To explore the acceptability of both the intervention and the trial design to participants and those delivering the intervention, and to assess whether the intervention was delivered with fidelity.

A process evaluation following Medical Research Council guidelines. Data collection included semi-structured interviews with participants and CTI caseworkers and observations of intervention delivery. A thematic analysis of interviews and observations was conducted to understand the intervention’s implementation and contextual factors as well as the trial process acceptability.

Participants for the pilot trial were recruited from three prisons in England and Wales where the intervention was being delivered.

While 28 out of 34 trial participants consented to interviews, only one was completed. Seven caseworkers were interviewed.

A housing-led CTI to support people leaving prison at risk of homelessness, involving phased, time-limited support from caseworkers, starting prerelease and continuing postrelease, to help secure stable housing and build independence, without directly providing housing.

The intervention’s acceptability was primarily reflected through the positive feedback and success stories shared by CTI caseworkers, as well as observational data indicating high acceptance among service users. The trial design’s acceptability was challenged by concerns about randomisation and equipoise, with staff viewing randomisation as unethical due to limited support for vulnerable populations. The fidelity to the CTI intervention housing-led approach was adhered to as best as possible; stable housing was prioritised for service users before addressing other needs. Despite these efforts, both sites encountered significant challenges due to limited housing availability and complex systems for securing social housing, particularly for single men leaving prison.

This wider study faced significant challenges which impacted the process evaluation. Despite these issues, the evaluation provides important insights into the challenges of conducting trials on interventions for people leaving prison. The challenges experienced should inform future study designs with similar populations and in similar settings.

ISRCTN46969988.

To determine whether a full-scale randomised control trial (RCT) assessing the efficacy and cost-effectiveness of a housing led Critical Time Intervention (CTI) is feasible and acceptable.

Pilot parallel two-arm individual level RCT, including process evaluation and embedded exploratory health economic evaluation.

Four prisons for men across England and Wales, UK.

Men leaving prison at risk of homelessness and intervention delivery staff.

CTI has four components: (1) pre-engagement phase: assessing the needs of the client and implementing a plan pre-discharge; (2) transition to community: forming relationships and goal setting; (3) try out: encouraging problem-solving and managing practical issues and (4) transfer of care: developing long-term goals and transferring responsibilities to community providers.

Progression criteria: recruitment, retention, acceptability of the processes (CTI and trial method) and fidelity of intervention delivery. We also assessed the completeness of primary, secondary and exploratory outcome measures and estimated intervention costs.

The recruitment progression criterion was met, with 92% (34/37) of approached individuals consenting to participate (target: 50%). However, the overall recruitment target of 80 was not achieved, and retention was low, only 18% (6/34) provided follow-up data, well below the 60% threshold. Retention was hindered by systemic challenges, including changes to prison release policies and reduced probation support. While the CTI model was acceptable to staff and service users, the trial design, particularly randomisation, was not. Intervention fidelity met the progression criteria. Baseline data collection for health economics and resource use was feasible, and intervention costs were estimated.

This pilot trial identified significant challenges to conducting a full-scale RCT of CTI in this context, particularly around retention, trial acceptability and systemic instability. While CTI remains a promising model, a traditional RCT design may not be viable in this setting without substantial structural and ethical adaptations.

ISRCTN46969988.

To estimate condition-specific patient travel distances and associated carbon emissions across common chronic diseases in routine National Health Service (NHS) care, and to assess the potential carbon savings of modal shifts in transportation.

Retrospective population-based cohort study.

NHS Greater Glasgow and Clyde, Scotland.

6599 patients aged 50–55 years at diagnosis, including cardiovascular disease (n=1711), epilepsy (n=1044), cancer (n=716), rheumatoid arthritis (RA; n=172) and a matched control group based on age, sex and area-level deprivation (n=2956).

Annual home-to-clinic distances and associated carbon emissions modelled under four transport modes (petrol car, electric car, bus, train) across five time points: 2-year prediagnosis, diagnosis year and 2-year postdiagnosis.

Mean annual travel distances to hospital varied by condition and peaked at diagnosis. Patients with cancer had the highest travel distances (161 km/patient/year for men; 139 km/patient/year for women), followed by RA (approximately 78 km/patient/year). The matched control group travelled 2/patient/year to 8.0 kg CO₂/patient/year. Bus travel resulted in intermediate emissions, estimated between 10.5 and 8.0 kg CO₂/patient. When travel was modelled using electric vehicles, emissions dropped between 3.5 and 2.7 kg for all conditions. Train travel produced similarly low emissions. Reducing petrol car travel from 100% to 60% lowered emissions up to 6.6 kg CO₂/patient.

Condition-specific estimates of healthcare-related travel emissions provide baseline understanding of the opportunities and challenges for decarbonising healthcare. Emission reduction is most achievable through modal shift, yet such shifts depend on factors beyond NHS control—such as transport infrastructure, digital access and social equity. Multisectoral strategies, including targeted telemedicine and integrated transport and urban planning, are critical to achieving net-zero healthcare while maintaining equitable access to care.