Liam Halligan unfolds the story of Carillion, the UK's second-largest construction firm built on billions of pounds of public money that imploded in January this year: a collapse that Labour leader Jeremy Corbyn called 'a watershed moment'. Using new testimony from insiders across the City and Whitehall, as well as Carillion itself, Halligan's investigation reveals that Carillion constructed a fortress of phony profits, while hiding mounting debts with aggressive accounting.