6 In examining these issues, we drew on a variety of evidence sources:
• we interviewed key individuals from the Department of Health & Social Care, the IPA, NHS England & NHS Improvement (NHSE&I), HM Treasury and the two NHS Trusts, to understand the chain of events and decisions before and after Carillion's liquidation and to check our understanding of written evidence;
• we checked the accuracy of statements in the report with third parties involved in the financing and construction of the two hospitals. We were unable to interview Carillion staff as our fieldwork started after Carillion had gone into liquidation;
• we reviewed documents, including business cases, contracts and contract schedules, ministerial briefings, meeting minutes from the two Trusts, emails between the Trusts and the Departments, and professional reports; and
• we analysed published and unpublished data. This included calculations and assessments made on the value for money of different options for completing the hospitals, data and calculations supporting business cases, and data used for calculating termination agreements. We did not independently verify these data. We set out our assumptions in notes to the Figures in this report.