Horizon was raised in Parliament in 2012.
CW report in 2014. PO discontinued prosecutions in 2015. Civil litigation in 2017—2019.
Inquiry was set up in 2020. In 2021, Court of Appeal quashed a large number of convictions.
Turns out, the combined power of investigative journalism, Parliament, the courts, and public inquiries aren't enough to prompt the government to actually do anything about the biggest miscarriage of justice in English legal history—that requires an ITV drama, apparently.